What additive can I add to Jelly Wax/Gel Wax to increase its cooling time/setting time? Jelly Wax. Jelly wax, also commonly known as gel wax, is a clear, dimensionally stable, jelly-like material made from specially processed mineral oils. It can be used to create a variety of special effects and is also suitable for making decorative container candles. It is normally heated until it liquifies and then poured into a mould. It sets quickly back into a jelly. 

I want to use it to pour into a transparent PVC pipe for a sculpture. Unfortunately I have found that it cools rather quickly for it to be useful for this purpose.

Anyone knows how I can increase the cooling time, using an additive maybe?
At your own risk, you can try using plasticizers for waxes. Usually, these plasticizers are wax esters of palmitic acid (well-known example is spermaceti, which can be replaced with jojoba oil, or you can buy/obtain those esters). But it's hard to predict exact amount of plasticizer needed. Add too much - and it will be creamy I-will-never-cool substance. I hope we have chemical engineers here who know more about wax plasticizers and can add details to my superficial statement.