Product Dissatisfaction

<p> My husband bought 20l of Pool paint on the 31/08/2016 from the store in Greenstone...e opened it used it and then close it lid on tightly and the next day when he opened to complete the painting the paint was rock hard....no-one at the store advised him of this neither is it anywhere on the product that this would happen...He added water to try make it weak so he could paint now we have dark blue walls with a white floor....Im so disappointed we paid R900 for this product and obviously visit builders for DIY stuff we not experts why dont things like this come with warnings????R900 down the drain</p>