I have owned a pot of this starch for over five years and it is just coming to an end. I have found it to be brilliant for starching traditional linen napkins. My pot has the instructions on the side. Wash article and spin. Dissolve four level scoops of starch in a little cold water. [You need to make sure that you have a solution that is like thick cream. The starch is an odd substance and it takes quite a bit of water to get this but add as little cold water as possible.] Add boiling water, stiring continually, to make a thick glue-like paste. [I make my starch in a very large jug and tend to add up to one litre of boiling water. You have to take care not to let it go lumpy]. The instructions then suggest adding a further litre of cold water but for napkins I find that another five litres mean that the napkins are not too stiff. You soak the articles in the starch, spin them and then let them dry out. They need to be ironed whilst still slightly damp.
The whole process is time consuming, especially as I do around 30 napkins in one go (but they then last for many months). However, nothing beats a well ironed and starched napkin and I love them. As an aside, linen napkins are very expensive. I have inherited many of mine from great aunts etc and some are over sixty years old. I have also bought them from the USA via eBay.