Equity Method Investments and Joint Ventures Disclosure [Text Block]

INVESTMENTS IN JOINT VENTURES

The financial statements of the Company’s foreign joint ventures are initially prepared using the accounting principles accepted in the respective joint ventures’ countries of domicile. Amounts related to foreign joint ventures reported in the below tables and the accompanying consolidated financial statements have subsequently been adjusted to conform with accounting principles generally accepted in the United States of America in all material respects. All material profits recorded on sales from the Company to its joint ventures and from joint ventures to other joint ventures have been eliminated for financial reporting purposes.

Financial information from the audited and unaudited financial statements of the Company’s joint ventures in Germany, Excor Korrosionsschutz – Technologien und Produkte GmbH (EXCOR), Harita-NTI LTD (India), Zerust OY (Finland) and all the Company’s other joint ventures, are summarized as follows:

	As of May 31, 2017
	Total		EXCOR		India		Finland		All Other
Current assets	$	48,064,624	$	19,820,904	$	4,322,253	$	1,929,781	$	21,991,686
Total assets		52,062,465		21,882,519		4,658,050		2,216,723		23,305,173
Current liabilities		13,773,839		3,028,386		1,412,054		547,007		8,786,392
Noncurrent liabilities		247,572		-		14,201		-		233,371
Joint ventures’ equity		38,041,054		18,854,133		3,231,795		1,669,716		14,285,410
Northern Technologies International Corporation’s share of joint ventures’ equity		18,903,473		9,427,068		1,615,898		834,856		7,025,651
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings		16,829,258		9,396,163		751,076		814,856		5,867,163

	Nine Months Ended May 31, 2017
	Total		EXCOR		India		Finland		All Other
Net sales	$	73,098,215	$	28,169,978	$	5,299,600	$	2,619,843	$	37,008,794
Gross profit		32,376,247		15,032,724		2,463,138		1,569,152		13,311,233
Net income		8,562,834		6,184,181		611,143		413,044		1,354,466
Northern Technologies International Corporation’s share of equity in income of joint ventures		4,343,159		3,089,935		384,712		206,874		661,638
Northern Technologies International Corporation's dividends received from joint ventures	$	5,179,786	$	4,240,400	$	446,939	$	200,768	$	291,679

	As of August 31, 2016
	Total		EXCOR		India		Finland		All Other
Current assets	$	48,922,924	$	22,928,810	$	4,027,016	$	1,928,861	$	20,038,237
Total assets		52,407,026		24,733,340		4,352,573		2,211,392		21,109,721
Current liabilities		12,433,700		3,485,213		1,097,231		546,506		7,304,730
Noncurrent liabilities		100,783		—		6,382		—		94,401
Joint ventures’ equity		39,872,543		21,248,109		3,248,960		1,664,886		13,710,588
Northern Technologies International Corporation’s share of joint ventures’ equity		19,840,774		10,624,056		1,624,480		832,442		6,759,796
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings		17,779,912		10,593,151		759,658		812,442		5,614,661

	Nine Months Ended May 31, 2016
	Total		EXCOR		India		Finland		All Other
Net sales	$	66,223,514	$	25,314,260	$	5,027,226	$	2,435,861	$	33,446,167
Gross profit		29,745,795		13,512,404		2,427,574		1,438,756		12,367,061
Net income		7,188,274		5,409,407		697,977		342,544		738,346
Northern Technologies International Corporation’s share of equity in income of joint ventures		3,600,884		2,714,905		327,846		171,662		386,471
Northern Technologies International Corporation's dividends received from joint ventures	$	5,449,543	$	4,364,700	$	326,023	$	206,516		552,304

The Company did

not

make any joint venture investments during the

nine

months ended

May 31, 2017

and

2016.

Note 7 - China Operations	9 Months Ended
Note 7 - China Operations	May 31, 2017
Notes to Financial Statements
Fair Value Disclosures [Text Block]	7. CHINA OPERATIONS Effective December 31, 2014, the Company terminated its joint venture agreements with its previous joint venture in China, Tianjin Zerust, began the process of liquidating the joint venture entity, and commenced operations in China through a wholly-owned subsidiary, NTIC (Shanghai) Co. Ltd. on January 1, 2015. Effective December 31, 2014, the Company’s investment in Tianjin Zerust was reported at carrying value based on the Company’s decreased level of influence over the entity, and the Company has reclassified previously unrecognized gains on foreign currency translation from accumulated other comprehensive income. Since it began the process of liquidating the joint venture entity on December 31, 2014, the Company has not received any proceeds from the assets of Tianjin Zerust. In addition, the Company has not received financial information or cooperation from its joint venture partner in determining the investment value. During the fourth quarter of fiscal 2016, the Company obtained additional information regarding the financial position of the investment through the legal proceedings that have been ongoing (See Note 13 ). These circumstances resulted in the Company concluding an indication of impairment existed and that the fair value of the investment was $0 as of August 31, 2016 based on accounting principles generally accepted in the United States of America. See Note 13 regarding ongoing litigation involving Tianjin Zerust.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Note 8 - Corporate Debt	9 Months Ended
Note 8 - Corporate Debt	May 31, 2017
Notes to Financial Statements
Debt Disclosure [Text Block]	8. CORPORATE DEBT The Company has a revolving line of credit with PNC Bank, National Association (PNC Bank) of $3,000,000. No amounts were outstanding under the line of credit as of both May 31, 2017 and August 31, 2016. At the option of the Company, outstanding advances under the line of credit bear interest at either (a) an annual rate based on LIBOR plus 2.15% for the applicable LIBOR interest period selected by the Company or (b) at the rate publicly announced by PNC Bank from time to time as its prime rate. Interest is payable in arrears (a) for the portion of advances bearing interest under the prime rate on the last day of each month during the term thereof and (b) for the portion of advances bearing interest under the LIBOR option on the last day of the respective LIBOR interest period selected for such advance. Any unpaid interest is payable on the maturity date. The revolving line of credit is secured by cash, receivables and inventory. The revolving credit facility allows the Company to request that PNC Bank issue letters of credit up to $1,200,000. The Company did not have any letters of credit reserved against the available letters of credit balance as of May 31, 2017 and August 31, 2016 with PNC Bank. The availability of advances under the line of credit will be reduced by the face amount of any letter of credit issued and outstanding (whether or not drawn) under the revolving credit facility. On January 11, 2017, the Company and PNC Bank extended the maturity date of the line of credit to January 7, 2018. All other terms of the line of credit and the loan agreement and other documents evidencing the line of credit remain the same. As of May 31, 2017 and August 31, 2016, the Company had $75,201 and $71,599, respectively, of letters of credit with JP Morgan Chase Bank that are performance based and set to expire between 2020 and 2022.

Note 9 - Stockholders' Equity	9 Months Ended
Note 9 - Stockholders' Equity	May 31, 2017
Notes to Financial Statements
Stockholders' Equity Note Disclosure [Text Block]	9. STOCKHOLDERS’ EQUITY During the nine months ended May 31, 2017, the Company repurchased and retired 14,525 shares of its common stock at a price of $13.51 per share. During the nine months ended May 31, 2017, stock options to purchase an aggregate of 4,000 shares of common stock at an exercise price of $10.25 per share were exercised. During the nine months ended May 31, 2017, the Company granted stock options under the Northern Technologies International Corporation Amended and Restated 2007 Stock Incentive Plan (the 2007 Plan) to purchase an aggregate of 56,677 shares of its common stock to various employees and directors. The weighted average per share exercise price of the stock options was $13.40, which was equal to the fair market value of the Company’s common stock on the date of grant. During the nine months ended May 31, 2016, the Company repurchased and retired 7,511 shares of its common stock at a price of $12.98 per share. During the nine months ended May 31, 2016, no stock options to purchase shares of common stock were exercised. During the nine months ended May 31, 2016, the Company granted stock options under the 2007 Plan to purchase an aggregate of 53,447 shares of its common stock to various employees and directors. The weighted average per share exercise price of the stock options was $14.85, which is equal to the fair market value of the Company’s common stock on the date of grant.

Note 10 - Net Income Per Common Share

9 Months Ended

May 31, 2017

Earnings Per Share [Text Block]

10.

NET INCOME PER COMMON SHARE

Basic net income per common share is computed by dividing net income by the weighted average number of common shares outstanding. Diluted net income per share assumes the exercise of stock options using the treasury stock method, if dilutive.

The following is a reconciliation of the net income per share computation for the

three

and

nine

months ended

May 31, 2017

and

2016:

	Three Months Ended				Nine Months Ended
Numerators:	May 31, 2017		May 31, 2016		May 31, 2017		May 31, 2016
Net income attributable to NTIC	$	1,352,416	$	917,373	$	2,037,021	$	575,233
Denominators:
Basic – weighted shares outstanding		4,526,771		4,538,970		4,528,523		4,538,005
Weighted shares assumed upon exercise of stock options		64,756		24,831		42,872		49,059
Diluted – weighted shares outstanding		4,591,527		4,563,801		4,571,395		4,587,064
Basic income per share:	$	0.30	$	0.20	$	0.45	$	0.13
Diluted income per share:	$	0.30	$	0.20	$	0.45	$	0.13

The dilutive impact summarized above relates to the periods when the average market price of the Company’s common stock exceeded the exercise price of the potentially dilutive option securities granted. Earnings per common share were based on the weighted average number of common shares outstanding during the periods when computing the basic earnings per share. When dilutive, stock options are included as equivalents using the treasury stock market method when computing the diluted earnings per share. There were

271,791

options outstanding as of

May 31, 2017,

that were dilutive.

Excluded from the computation of diluted income per share for the

three

and

nine

months ended

May 31, 2017

were options outstanding to purchase

48,067

shares of common stock. Excluded from the computation of diluted earnings per share for the

three

and

nine

months ended

May 31, 2016

were options outstanding to purchase

170,887

shares of common stock.

Note 11 - Stock-based Compensation

9 Months Ended

May 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Text Block]

11.

STOCK-BASED COMPENSATION

The Company has

two

stock-based compensation plans under which stock options and other stock-based awards have been granted, the Northern Technologies International Corporation Amended and Restated

2007

Stock Incentive Plan and the Northern Technologies International Corporation Employee Stock Purchase Plan (the ESPP). The Compensation Committee of the Board of Directors and the Board of Directors administer these plans.

The

2007

Plan provides for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock, stock unit awards, performance awards and stock bonuses to eligible recipients to enable the Company and its subsidiaries to attract and retain qualified individuals through opportunities for equity participation in the Company, and to reward those individuals who contribute to the achievement of the Company’s economic objectives. Subject to adjustment as provided in the

2007

Plan, up to a maximum of

800,000

shares of the Company’s common stock are issuable under the

2007

Plan. Options granted under the

2007

Plan generally have a term of

ten

years and become exercisable over a

three

- or

four

-year period beginning on the

one

-year anniversary of the date of grant. Options are granted at per share exercise prices equal to the market value of the Company’s common stock on the date of grant. The Company issues new shares upon the exercise of options. As of

May 31, 2017,

only stock options and stock bonuses had been granted under the

2007

Plan.

The maximum number of shares of common stock of the Company available for issuance under the ESPP is

100,000

shares, subject to adjustment as provided in the ESPP. The ESPP provides for

six

-month offering periods beginning on

September 1

and

March 1

of each year. The purchase price of the shares is

90%

of the lower of the fair market value of common stock at the beginning or end of the offering period. This discount

may

not

exceed the maximum discount rate permitted for plans of this type under Section

423

of the Internal Revenue Code of

1986,

as amended. The ESPP is compensatory for financial reporting purposes.

The Company granted options to purchase an aggregate of

56,677

and

53,447

shares of its common stock during the

nine

months ended

May 31, 2017

and

2016,

respectively. The fair value of option grants is determined at date of grant, using the Black-Scholes option pricing model with the assumptions listed below. The Company recognized compensation expense of

$293,748

and

$325,576

during the

nine

months ended

May 31, 2017

and

2016,

respectively, related to the options that vested during such time period. As of

May 31, 2017,

the total compensation cost for non-vested options

not

yet recognized in the Company’s consolidated statements of operations was

$337,316,

net of estimated forfeitures. Stock-based compensation expense of

$97,916

is expected through the remainder of fiscal year

2017,

and

$159,600

and

$79,800

is expected to be recognized during fiscal

2018

and fiscal

2019,

respectively, based on outstanding options as of

May 31, 2017.

Future option grants will impact the compensation expense recognized. Stock-based compensation expense is included in general and administrative expense on the consolidated statements of operations.

The fair value of each option grant is estimated on the grant date using the Black-Scholes option-pricing model with the following assumptions and results for the grants:

	Nine Months Ended
	May 31, 2017			May 31, 2016
Dividend yield		0.00	%		0.00	%
Expected volatility		46.4	%		46.0	%
Expected life of option (in years)		10			10
Average risk-free interest rate		1.63	%		1.63	%

The weighted average per share fair value of options granted during

nine

months ended

May 31, 2017

and

2016

was

$7.69

and

$8.48,

respectively. The weighted average remaining contractual life of the options outstanding as of

May 31, 2017

and

2016

was

6.73

years and

6.71

years, respectively.

Note 12 - Segment and Geographic Information

9 Months Ended

May 31, 2017

Segment Reporting Disclosure [Text Block]

12.

SEGMENT AND GEOGRAPHIC INFORMATION

Segment Information

The Company’s chief operating decision maker (CODM) is its Chief Executive Officer. The Company’s business is organized into

two

reportable segments: ZERUST® and Natur-Tec®. The Company has been selling its proprietary ZERUST® rust and corrosion inhibiting products and services to the automotive, electronics, electrical, mechanical, military and retail consumer markets for over

years, and more recently, has targeted and expanded into the oil and gas industry. The Company also sells a portfolio of bio-based and compostable (fully biodegradable) polymer resins and finished products under the Natur-Tec® brand.

The following table sets forth the Company’s net sales for the

three

and

nine

months ended

May 31, 2017

and

2016

by segment:

	Three Months Ended				Nine Months Ended
	May 31, 2017		May 31, 2016		May 31, 2017		May 31, 2016
ZERUST® net sales	$	8,368,487	$	7,185,955	$	23,681,192	$	19,548,974
Natur-Tec® net sales		1,854,532		1,500,620		4,986,753		3,866,972
Total net sales	$	10,223,019	$	8,686,575	$	28,667,945	$	23,415,946

The following table sets forth the Company’s cost of goods sold for the

three

and

nine

months ended

May

31,

2017

and

2016

by segment:

	Three Months Ended										Nine Months Ended
	May 31, 2017		% of Segment Sales*			May 31, 2016		% of Segment Sales*			May 31, 2017		% of Segment Sales*			May 31, 2016		% of Segment Sales*
Direct cost of goods sold
ZERUST®	$	4,834,355		57.8	%	$	4,028,114		56.1	%	$	13,788,416		58.2	%	$	10,968,742		56.1	%
Natur-Tec®		1,327,323		71.6	%		1,119,730		74.6	%		3,608,722		72.4	%		2,938,927		76.0	%
Indirect cost of goods sold		612,323		—			629,405		—			1,859,815		—			2,013,227		—
Total net cost of goods sold	$	6,774,001				$	5,777,249				$	19,256,953				$	15,920,896

____________________________

The percent of segment sales is calculated by dividing the direct cost of goods sold for each individual segment category by the net sales for each segment category.

The Company utilizes product net sales and direct and indirect cost of goods sold for each product in reviewing the financial performance of a product type. Further allocation of Company expenses or assets, aside from amounts presented in the tables above, is

not

utilized in evaluating product performance, nor does such allocation occur for internal financial reporting.

Geographic Information

Net sales by geographic location for the

three

and

nine

months ended

May 31, 2017

and

2016

were as follows:

	Three Months Ended				Nine Months Ended
	May 31, 2017		May 31, 2016		May 31, 2017		May 31, 2016
Inside the U.S.A. to unaffiliated customers	$	5,967,459	$	5,559,885	$	16,363,291	$	14,762,170
Outside the U.S.A. to:
Joint ventures in which the Company is a shareholder directly and indirectly		862,136		446,322		2,115,511		1,967,370
Unaffiliated customers		3,393,424		2,680,368		10,189,143		6,686,406
	$	10,223,019	$	8,686,575	$	28,667,945	$	23,415,946

Net sales by geographic location are based on the location of the customer. Fees for services provided to joint ventures by geographic location as a percentage of total fees for services provided to joint ventures during the

three

and

nine

months ended

May 31, 2017

and

2016

were as follows:

	Three Months Ended
	May 31, 2017		% of Total Fees for Services Provided to Joint Ventures			May 31, 2016		% of Total Fees for Services Provided to Joint Ventures
Germany	$	212,257		14.7	%	$	242,158		17.9	%
Poland		180,969		12.6	%		167,237		12.4	%
Japan		153,903		10.7	%		148,091		11.0	%
Sweden		150,139		10.4	%		66,239		4.9	%
France		112,455		7.8	%		87,588		6.5	%
Thailand		104,771		7.3	%		132,548		9.8	%
Korea		92,954		6.4	%		74,085		5.5	%
India		90,469		6.3	%		70,610		5.2	%
United Kingdom		87,768		6.1	%		135,068		10.0	%
Finland		78,012		5.4	%		55,876		4.1	%
Czech Republic		74,135		5.1	%		54,537		4.0	%
Other		104,216		7.2	%		117,876		8.7	%
	$	1,442,048		100.0	%	$	1,351,913		100.0	%

	Nine Months Ended
	May 31, 2017		% of Total Fees for Services Provided to Joint Ventures			May 31, 2016		% of Total Fees for Services Provided to Joint Ventures
Germany	$	614,766		15.6	%	$	664,812		17.4	%
Poland		483,626		12.3	%		452,260		11.8	%
Japan		445,662		11.3	%		416,241		10.9	%
Thailand		339,852		8.6	%		395,611		10.4	%
Sweden		314,664		8.0	%		189,556		5.0	%
France		293,240		7.4	%		250,373		6.6	%
Korea		284,435		7.2	%		247,730		6.5	%
India		229,200		5.8	%		223,137		5.9	%
United Kingdom		227,140		5.8	%		292,216		7.7	%
Finland		221,294		5.6	%		177,704		4.7	%
Czech Republic		218,249		5.5	%		176,470		4.6	%
Other		269,539		6.9	%		322,274		8.5	%
	$	3,941,667		100.0	%	$	3,808,384		100.0	%

Sales to the Company’s joint ventures are included in the foregoing segment and geographic information, however, sales by the Company’s joint ventures to other parties are

not

included. The foregoing segment and geographic information represents only sales and cost of goods sold recognized directly by the Company.

The geographical distribution of key financial statement data is as follows:

	At May 31, 2017		At August 31, 2016
Brazil	$	56,246	$	66,938
India		13,634		13,645
Germany		13,687		—
China		231,114		253,931
United States		7,137,218		6,941,358
Total long-lived assets	$	7,451,899	$	7,275,872

	Nine Months Ended
	May 31, 2017		May 31, 2016
Brazil	$	1,683,255	$	1,509,659
India		1,057,132		911,227
Germany		378,635		—
China		4,991,807		2,473,733
United States		20,557,116		18,521,327
Total net sales	$	28,667,945	$	23,415,946

Total long-lived assets located in Brazil, India, Germany and China primarily consist of property and equipment. These assets are periodically reviewed to assure the net realizable value from the estimated future production based on forecasted sales exceeds the carrying value of the assets. Total assets located in the United States include the Company’s investments in joint ventures.

Sales to the Company’s joint ventures are included in the foregoing segment and geographic information; however, sales by the Company’s joint ventures to other parties are

not

included. The foregoing segment and geographic information represents only sales and cost of goods sold recognized directly by the Company.

All joint venture operations including equity in income, fees for services and related dividends are related to ZERUST® products and services.

Note 13 - Commitments and Contingencies	9 Months Ended
Note 13 - Commitments and Contingencies	May 31, 2017
Notes to Financial Statements
Commitments and Contingencies Disclosure [Text Block]	13. COMMITMENTS AND CONTINGENCIES On August 26, 2016, the Compensation Committee of the Board of Directors of the Company approved the material terms of an annual bonus plan for the Company’s executive officers as well as certain officers and employees for the fiscal year ending August 31, 2017. For fiscal 2017 as in past years, the total amount available under the bonus plan for all plan participants, including executive officers, is dependent upon the Company’s earnings before interest, taxes and other income, as adjusted to consider amounts to be paid under the bonus plan and certain other adjustments (Adjusted EBITOI). Each plan participant’s percentage of the overall bonus pool is based upon the number of plan participants, the individual’s annual base salary and the individual’s position and level of responsibility within the company. In the case of each of the Company’s executive officer participants, 75% of the amount of their individual bonus payout will be determined based upon the Company’s actual Adjusted EBITOI for fiscal 2017 compared to a pre-established target Adjusted EBITOI for fiscal 2017 and 25% of the payout will be determined based upon such executive officer’s achievement of certain pre-established individual performance objectives. The payment of bonuses under the plan are discretionary and may be paid to executive officer participants in both cash and shares of the Company’s common stock, the exact amount and percentages will be determined by the Company’s Board of Directors, upon recommendation of the Compensation Committee, after the completion of the Company’s consolidated financial statements for fiscal 2017. There was $600,000 accrued for management bonuses for the nine months ended May 31, 2017 compared to an accrual of $215,000 for management bonuses for the nine months ended May 31, 2016. Two joint ventures (consisting of the Company’s joint ventures in Korea and India) accounted for 21.4% of the Company’s trade joint venture receivables at May 31, 2017, and three joint ventures (consisting of the Company’s joint ventures in Korea, India and Thailand) accounted for 55.8% of the Company’s trade joint venture receivables as of August 31, 2016. On March 23, 2015, the Company and NTI Asean LLC (NTI Asean) filed a lawsuit in Tianjin No 1 Intermediate People’s Court against two individuals, Tao Meng and Xu Hui, related to breaches of duties and contractual commitments owed to NTI Asean under certain agreements related to the Company’s former joint venture in China, Tianjin Zerust Anti-Corrosion Technologies Ltd. (Tianjin Zerust). The lawsuit alleges, among other things, that Mr. Tao Meng and Xu Hui have engaged in self-dealing, usurped business opportunities, and received economic benefits that were required to go to Tianjin Zerust. As of May 31, 2017, the Company is not able to reasonably estimate the amount of any recovery to NTI Asean, if any. On April 21, 2015, the Company and NTI Asean initiated a lawsuit in the District Court for the Second Judicial District, County of Ramsey, State of Minnesota against Cortec Corporation alleging, among other things, that Cortec Corporation (Cortec) aided and abetted breaches of duties and contractual commitments owed to the Company and NTI Asean related to the Company’s joint venture in China, Tianjin Zerust. After fully litigating the case through discovery and dispositive motion practice, on February 16, 2017, the Minnesota court denied both sides’ motions for summary judgment and, sua sponte , dismissed without prejudice the Company’s and NTI Asean’s claims based on a non-exclusive forum-selection clause contained in a 2005 settlement agreement between the Company and Cortec Corporation. While the Company had strong arguments to appeal the Minnesota court’s decision, an appeal would have meant a significant delay to the resolution of the dispute. On April 21, 2017, the Company re-filed the lawsuit in the United States District Court for the Northern District of Ohio. On May 15, 2017, Cortec filed an answer and counterclaim. The counterclaim was promptly dismissed by the Court. Cortec has agreed that all the discovery and information learned in the Minnesota case may be used in the Ohio case. The parties attended a Case Management Conference (CMC) on June 21, 2017. The Court set a deadline of September 4, 2017 to complete discovery and set the case for a jury trial on a two -week standby period beginning on September 18, 2017. From time to time, the Company is subject to various other claims and legal actions in the ordinary course of its business. The Company records a liability in its consolidated financial statements for costs related to claims, including future legal costs, settlements and judgments, where the Company has assessed that a loss is probable and an amount can be reasonably estimated. If the reasonable estimate of a probable loss is a range, the Company records the most probable estimate of the loss or the minimum amount when no amount within the range is a better estimate than any other amount. The Company discloses a contingent liability even if the liability is not probable or the amount is not estimable, or both, if there is a reasonable possibility that material loss may be have been incurred. In the opinion of management, as of May 31, 2017, the amount of liability, if any, with respect to these matters, individually or in the aggregate, will not materially affect the Company’s consolidated results of operations, financial position or cash flows.

Note 14 - Fair Value Measurements

9 Months Ended

May 31, 2017

Fair Value, Measurement Inputs, Disclosure [Text Block]

14.

Fair Value Measurements

Assets and liabilities that are measured at fair value on a recurring basis primarily relate to marketable equity securities. These items are marked-to-market at each reporting period.

The following tables provide information by level for assets and liabilities that are measured at fair value on a recurring basis:

			Fair Value Measurements Using Inputs Considered as
	Fair Value as of May 31, 2017		Level 1		Level 2		Level 3
Available for sale securities	$	3,756,680	$	3,756,680	$	—	$	—

			Fair Value Measurements Using Inputs Considered as
	Fair Value as of August 31, 2016		Level 1		Level 2		Level 3
Available for sale securities	$	2,243,864	$	2,243,864	$	—	$	—

There were

transfers between Level

Level

or Level

during the

three

and

nine

months ended

May

31,

2017

and

2016.

Note 3 - Inventories (Tables)

9 Months Ended

May 31, 2017

Schedule of Inventory, Current [Table Text Block]

	May 31, 2017		August 31, 2016
Production materials	$	1,454,328	$	1,452,396
Finished goods		6,425,328		6,258,891
	$	7,879,656	$	7,711,287

Note 6 - Investments in Joint Ventures (Tables)

9 Months Ended

May 31, 2017

Condensed Balance Sheet [Table Text Block]

	As of May 31, 2017
	Total		EXCOR		India		Finland		All Other
Current assets	$	48,064,624	$	19,820,904	$	4,322,253	$	1,929,781	$	21,991,686
Total assets		52,062,465		21,882,519		4,658,050		2,216,723		23,305,173
Current liabilities		13,773,839		3,028,386		1,412,054		547,007		8,786,392
Noncurrent liabilities		247,572		-		14,201		-		233,371
Joint ventures’ equity		38,041,054		18,854,133		3,231,795		1,669,716		14,285,410
Northern Technologies International Corporation’s share of joint ventures’ equity		18,903,473		9,427,068		1,615,898		834,856		7,025,651
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings		16,829,258		9,396,163		751,076		814,856		5,867,163

	As of August 31, 2016
	Total		EXCOR		India		Finland		All Other
Current assets	$	48,922,924	$	22,928,810	$	4,027,016	$	1,928,861	$	20,038,237
Total assets		52,407,026		24,733,340		4,352,573		2,211,392		21,109,721
Current liabilities		12,433,700		3,485,213		1,097,231		546,506		7,304,730
Noncurrent liabilities		100,783		—		6,382		—		94,401
Joint ventures’ equity		39,872,543		21,248,109		3,248,960		1,664,886		13,710,588
Northern Technologies International Corporation’s share of joint ventures’ equity		19,840,774		10,624,056		1,624,480		832,442		6,759,796
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings		17,779,912		10,593,151		759,658		812,442		5,614,661

Condensed Income Statement [Table Text Block]

	Nine Months Ended May 31, 2017
	Total		EXCOR		India		Finland		All Other
Net sales	$	73,098,215	$	28,169,978	$	5,299,600	$	2,619,843	$	37,008,794
Gross profit		32,376,247		15,032,724		2,463,138		1,569,152		13,311,233
Net income		8,562,834		6,184,181		611,143		413,044		1,354,466
Northern Technologies International Corporation’s share of equity in income of joint ventures		4,343,159		3,089,935		384,712		206,874		661,638
Northern Technologies International Corporation's dividends received from joint ventures	$	5,179,786	$	4,240,400	$	446,939	$	200,768	$	291,679

	Nine Months Ended May 31, 2016
	Total		EXCOR		India		Finland		All Other
Net sales	$	66,223,514	$	25,314,260	$	5,027,226	$	2,435,861	$	33,446,167
Gross profit		29,745,795		13,512,404		2,427,574		1,438,756		12,367,061
Net income		7,188,274		5,409,407		697,977		342,544		738,346
Northern Technologies International Corporation’s share of equity in income of joint ventures		3,600,884		2,714,905		327,846		171,662		386,471
Northern Technologies International Corporation's dividends received from joint ventures	$	5,449,543	$	4,364,700	$	326,023	$	206,516		552,304

Note 12 - Segment and Geographic Information (Tables)

9 Months Ended

May 31, 2017

Reconciliation of Cost of Goods Sold from Segments to Consolidated [Table Text Block]

	Three Months Ended										Nine Months Ended
	May 31, 2017		% of Segment Sales*			May 31, 2016		% of Segment Sales*			May 31, 2017		% of Segment Sales*			May 31, 2016		% of Segment Sales*
Direct cost of goods sold
ZERUST®	$	4,834,355		57.8	%	$	4,028,114		56.1	%	$	13,788,416		58.2	%	$	10,968,742		56.1	%
Natur-Tec®		1,327,323		71.6	%		1,119,730		74.6	%		3,608,722		72.4	%		2,938,927		76.0	%
Indirect cost of goods sold		612,323		—			629,405		—			1,859,815		—			2,013,227		—
Total net cost of goods sold	$	6,774,001				$	5,777,249				$	19,256,953				$	15,920,896

Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area [Table Text Block]

	Three Months Ended				Nine Months Ended
	May 31, 2017		May 31, 2016		May 31, 2017		May 31, 2016
Inside the U.S.A. to unaffiliated customers	$	5,967,459	$	5,559,885	$	16,363,291	$	14,762,170
Outside the U.S.A. to:
Joint ventures in which the Company is a shareholder directly and indirectly		862,136		446,322		2,115,511		1,967,370
Unaffiliated customers		3,393,424		2,680,368		10,189,143		6,686,406
	$	10,223,019	$	8,686,575	$	28,667,945	$	23,415,946

Reconciliation of Revenue from Segments to Consolidated [Table Text Block]

	Three Months Ended				Nine Months Ended
	May 31, 2017		May 31, 2016		May 31, 2017		May 31, 2016
ZERUST® net sales	$	8,368,487	$	7,185,955	$	23,681,192	$	19,548,974
Natur-Tec® net sales		1,854,532		1,500,620		4,986,753		3,866,972
Total net sales	$	10,223,019	$	8,686,575	$	28,667,945	$	23,415,946

Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block]

	At May 31, 2017		At August 31, 2016
Brazil	$	56,246	$	66,938
India		13,634		13,645
Germany		13,687		—
China		231,114		253,931
United States		7,137,218		6,941,358
Total long-lived assets	$	7,451,899	$	7,275,872

Revenue from External Customers by Geographic Areas [Table Text Block]

	Nine Months Ended
	May 31, 2017		May 31, 2016
Brazil	$	1,683,255	$	1,509,659
India		1,057,132		911,227
Germany		378,635		—
China		4,991,807		2,473,733
United States		20,557,116		18,521,327
Total net sales	$	28,667,945	$	23,415,946

Fees for Services Provided to Joint Ventures [Member]

Reconciliation of Revenue from Segments to Consolidated [Table Text Block]

	Three Months Ended
	May 31, 2017		% of Total Fees for Services Provided to Joint Ventures			May 31, 2016		% of Total Fees for Services Provided to Joint Ventures
Germany	$	212,257		14.7	%	$	242,158		17.9	%
Poland		180,969		12.6	%		167,237		12.4	%
Japan		153,903		10.7	%		148,091		11.0	%
Sweden		150,139		10.4	%		66,239		4.9	%
France		112,455		7.8	%		87,588		6.5	%
Thailand		104,771		7.3	%		132,548		9.8	%
Korea		92,954		6.4	%		74,085		5.5	%
India		90,469		6.3	%		70,610		5.2	%
United Kingdom		87,768		6.1	%		135,068		10.0	%
Finland		78,012		5.4	%		55,876		4.1	%
Czech Republic		74,135		5.1	%		54,537		4.0	%
Other		104,216		7.2	%		117,876		8.7	%
	$	1,442,048		100.0	%	$	1,351,913		100.0	%

	Nine Months Ended
	May 31, 2017		% of Total Fees for Services Provided to Joint Ventures			May 31, 2016		% of Total Fees for Services Provided to Joint Ventures
Germany	$	614,766		15.6	%	$	664,812		17.4	%
Poland		483,626		12.3	%		452,260		11.8	%
Japan		445,662		11.3	%		416,241		10.9	%
Thailand		339,852		8.6	%		395,611		10.4	%
Sweden		314,664		8.0	%		189,556		5.0	%
France		293,240		7.4	%		250,373		6.6	%
Korea		284,435		7.2	%		247,730		6.5	%
India		229,200		5.8	%		223,137		5.9	%
United Kingdom		227,140		5.8	%		292,216		7.7	%
Finland		221,294		5.6	%		177,704		4.7	%
Czech Republic		218,249		5.5	%		176,470		4.6	%
Other		269,539		6.9	%		322,274		8.5	%
	$	3,941,667		100.0	%	$	3,808,384		100.0	%

Note 3 - Inventories - Inventories (Details) - USD ($)	May 31, 2017	Aug. 31, 2016
Production materials	$ 1,454,328	$ 1,452,396
Finished goods	6,425,328	6,258,891
Inventories	$ 7,879,656	$ 7,711,287

Note 4 - Property and Equipment, Net - Components of Property and Equipment, Net (Details) - USD ($)	May 31, 2017	Aug. 31, 2016
Land	$ 310,365	$ 310,365
Buildings and improvements	6,623,104	6,528,252
Machinery and equipment	4,170,638	3,590,063
Gross	11,104,107	10,428,680
Less accumulated depreciation	(3,652,208)	(3,152,808)
Net	$ 7,451,899	$ 7,275,872

Note 5 - Patents and Trademarks, Net (Details Textual) - Patents and Trademarks [Member]	9 Months Ended
	May 31, 2017 USD ($)
Finite-Lived Intangible Asset, Useful Life	7 years
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	$ 120,000
Finite-Lived Intangible Assets, Amortization Expense, Year Five	120,000
Finite-Lived Intangible Assets, Amortization Expense, Year Two	120,000
Finite-Lived Intangible Assets, Amortization Expense, Year Three	120,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four	$ 120,000

Note 5 - Patents and Trademarks, Net - Patents and Trademarks, Net (Details) - USD ($)	May 31, 2017	Aug. 31, 2016
Patents and trademarkes, net	$ 1,314,103	$ 1,278,597
Patents and Trademarks [Member]
Patents and trademarks	2,700,215	2,575,435
Less accumulated amortization	(1,386,112)	(1,296,838)
Patents and trademarkes, net	$ 1,314,103	$ 1,278,597

Note 6 - Investments in Joint Ventures - Condensed Balance Sheet of EXCOR and All Other Joint Ventures (Details) - USD ($)	May 31, 2017	Aug. 31, 2016
Total assets	$ 52,062,465	$ 52,407,026
Current liabilities	13,773,839	12,433,700
Noncurrent liabilities	247,572	100,783
Joint ventures’ equity	38,041,054	39,872,543
Northern Technologies International Corporation’s share of joint ventures’ equity	18,903,473	19,840,774
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	16,829,258	17,779,912
Current assets	48,064,624	48,922,924
EXCOR [Member]
Total assets	21,882,519	24,733,340
Current liabilities	3,028,386	3,485,213
Noncurrent liabilities
Joint ventures’ equity	18,854,133	21,248,109
Northern Technologies International Corporation’s share of joint ventures’ equity	9,427,068	10,624,056
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	9,396,163	10,593,151
Current assets	19,820,904	22,928,810
Joint Venture in India [Member]
Total assets	4,658,050	4,352,573
Current liabilities	1,412,054	1,097,231
Noncurrent liabilities	14,201	6,382
Joint ventures’ equity	3,231,795	3,248,960
Northern Technologies International Corporation’s share of joint ventures’ equity	1,615,898	1,624,480
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	751,076	759,658
Current assets	4,322,253	4,027,016
Joint Venture in Finland [Member]
Total assets	2,216,723	2,211,392
Current liabilities	547,007	546,506
Noncurrent liabilities
Joint ventures’ equity	1,669,716	1,664,886
Northern Technologies International Corporation’s share of joint ventures’ equity	834,856	832,442
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	814,856	812,442
Current assets	1,929,781	1,928,861
All Other [Member]
Total assets	23,305,173	21,109,721
Current liabilities	8,786,392	7,304,730
Noncurrent liabilities	233,371	94,401
Joint ventures’ equity	14,285,410	13,710,588
Northern Technologies International Corporation’s share of joint ventures’ equity	7,025,651	6,759,796
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	5,867,163	5,614,661
Current assets	$ 21,991,686	$ 20,038,237

Note 6 - Investments in Joint Ventures - Condensed Income Statement of EXCOR and All Other Joint Ventures (Details) - USD ($)	3 Months Ended		9 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2017	May 31, 2016
Gross profit			$ 32,376,247	$ 29,745,795
Net income			8,562,834	7,188,274
Northern Technologies International Corporation’s share of equity in income of joint ventures	$ 1,686,016	$ 1,664,464	4,343,159	3,600,884
Northern Technologies International Corporation's dividends received from joint ventures			5,179,786	5,449,543
Net sales			73,098,215	66,223,514
EXCOR [Member]
Gross profit			15,032,724	13,512,404
Net income			6,184,181	5,409,407
Northern Technologies International Corporation’s share of equity in income of joint ventures			3,089,935	2,714,905
Northern Technologies International Corporation's dividends received from joint ventures			4,240,400	4,364,700
Net sales			28,169,978	25,314,260
Joint Venture in India [Member]
Gross profit			2,463,138	2,427,574
Net income			611,143	697,977
Northern Technologies International Corporation’s share of equity in income of joint ventures			384,712	327,846
Northern Technologies International Corporation's dividends received from joint ventures			446,939	326,023
Net sales			5,299,600	5,027,226
Joint Venture in Finland [Member]
Gross profit			1,569,152	1,438,756
Net income			413,044	342,544
Northern Technologies International Corporation’s share of equity in income of joint ventures			206,874	171,662
Northern Technologies International Corporation's dividends received from joint ventures			200,768	206,516
Net sales			2,619,843	2,435,861
All Other [Member]
Gross profit			13,311,233	12,367,061
Net income			1,354,466	738,346
Northern Technologies International Corporation’s share of equity in income of joint ventures			661,638	386,471
Northern Technologies International Corporation's dividends received from joint ventures			291,679	552,304
Net sales			$ 37,008,794	$ 33,446,167

Note 8 - Corporate Debt (Details Textual) - USD ($)	9 Months Ended
Note 8 - Corporate Debt (Details Textual) - USD ($)	May 31, 2017	Aug. 31, 2016
PNC Bank [Member]
Letters of Credit Outstanding, Amount	$ 0	$ 0
PNC Bank [Member] \| Revolving Credit Facility [Member]
Long-term Line of Credit	0	0
Line of Credit Facility, Maximum Borrowing Capacity	$ 3,000,000
PNC Bank [Member] \| Revolving Credit Facility [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate	2.15%
PNC Bank [Member] \| Letter of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,200,000
JP Morgan Chase Bank [Member]
Letters of Credit Outstanding, Amount	$ 75,201	$ 71,599

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References + Details

Note 9 - Stockholders' Equity (Details Textual) - $ / shares	9 Months Ended
	May 31, 2017	May 31, 2016
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 10.25
Stock Repurchased and Retired During Period, Shares	14,525	7,511
Treasury Stock Acquired, Average Cost Per Share	$ 13.51	$ 12.98
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	4,000	0
The 2007 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	56,677	53,447
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 13.40	$ 14.85

Note 10 - Net Income Per Common Share (Details Textual) - shares	3 Months Ended		9 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2017	May 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	271,791		271,791
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	48,067	170,887	48,067	170,887

Note 10 - Net Income Per Common Share - Reconciliation of the Earnings Per Share Computations (Details) - USD ($)	3 Months Ended		9 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2017	May 31, 2016
Net income attributable to NTIC	$ 1,352,416	$ 917,373	$ 2,037,021	$ 575,233
Basic – weighted shares outstanding (in shares)	4,526,771	4,538,970	4,528,523	4,538,005
Weighted shares assumed upon exercise of stock options (in shares)	64,756	24,831	42,872	49,059
Diluted – weighted shares outstanding (in shares)	4,591,527	4,563,801	4,571,395	4,587,064
Basic income per share: (in dollars per share)	$ 0.30	$ 0.20	$ 0.45	$ 0.13
Diluted income per share: (in dollars per share)	$ 0.30	$ 0.20	$ 0.45	$ 0.13

Note 11 - Stock-based Compensation (Details Textual)	9 Months Ended
Note 11 - Stock-based Compensation (Details Textual)	May 31, 2017 USD ($) $ / shares shares	May 31, 2016 USD ($) $ / shares shares
Number of Stock-based Compensation Plans	2
Stock or Unit Option Plan Expense	$ 293,748	$ 325,576
Allocated Share-based Compensation Expense, Estimate Remainder of Fiscal Year	97,916
Allocated Share-based Compensation Expense, Estimate, Next Fiscal Year	159,600
Allocated Share-based Compensation Expense, Estimate, Fiscal Year Two	$ 79,800
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares	$ 7.69	$ 8.48
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	6 years 266 days	6 years 259 days
Net of Estimated Forfeitures [Member]
Allocated Share-based Compensation Expense, Estimate Remainder of Fiscal Year	$ 337,316
The 2007 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized \| shares	800,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross \| shares	56,677	53,447
The 2007 Plan [Member] \| One Year after Date of Grant [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
The 2007 Plan [Member] \| One Year after Date of Grant [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized \| shares	100,000
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent	90.00%

Note 11 - Stock-based Compensation - Black-Scholes Option-pricing Model Assumptions (Details)	9 Months Ended
	May 31, 2017	May 31, 2016
Dividend yield	0.00%	0.00%
Expected volatility	46.40%	46.00%
Expected life of option (Year)	10 years	10 years
Average risk-free interest rate	1.63%	1.63%

Note 12 - Segment and Geographic Information - Cost of Goods Sold by Segment (Details) - USD ($)

3 Months Ended

9 Months Ended

May 31, 2017

May 31, 2016

May 31, 2017

May 31, 2016

^[1]

Direct Cost of Goods Sold [Member] | ZERUST [Member]

$ 6,774,001

$ 5,777,249

$ 19,256,953

$ 15,920,896

^[1]

57.80%

56.10%

58.20%

56.10%

Direct Cost of Goods Sold [Member] | NaturTec [Member]

$ 4,834,355

$ 4,028,114

$ 13,788,416

$ 10,968,742

^[1]

71.60%

74.60%

72.40%

76.00%

Indirect Cost of Goods Sold [Member]

$ 1,327,323

$ 1,119,730

$ 3,608,722

$ 2,938,927

^[1]