Poor customer service and unethical business practice

Purchase tar rejuvinating paint from the owner of this business. I needed to rejuvinate 540m2. His guide is 60m2 per 20lt bucket. Hence I would require 9 buckets to cover the area. I applied the product as per his instructions, and landed up having 4 (80lt spare). I requested that he take back the excess as it is not needed, and he refused, stating that the product is made to order. At no time before purchasing the product was I made aware of such condition. The consumer protection act states that the consumer must be made aware of all such conditions before the purchase, so that the consumer can make an informed decision on their purchase.

When I enquired why is the coverage so different to the guide he provided, he stated that on surfaces (if they are smooth) can get up to 80m2 per bucket. But he then stated that I have not applied the product as per his instructions (which I deny as I followed them to the letter). I requested several times that he substantiate his comments, which to date he has refused to do.

I strongly believe that this gent purposely understates the coverage of his product so inflate the volumes of product purchased. This is an unethical business practice and in contravention of the CPA. His refusal to take back the excess product is also not warranted, and the excuses he provided are "it is a sold product" and "I make to order" are not valid, as these were only communicated to me when I wanted to return the excess.

He has also not decided to take to Facebook to tarnish my reputation, and is threatening me with defamation etc. It is sad when a businessman cannot handle the truth and cannot admit that he is in the wrong.