http://www.nikwax.com/en-us/webquiz/index.php -take the quiz. You have to get the questions correct, but you can take the quiz again until you do. You can get samples from them every 2 months, it’s been over 2 months since this was last posted.

http://www.nikwax.com/enmygb/webquiz/index.php -you can also to the quiz on this page to get a free Cotton Proof Sample.