If you’ve printed with photopolymer resins, you know that you need alcohol. Lots of alcohol. It makes sense that people would like to reuse the alcohol both to be environmentally responsible and to save a little money. The problem is that the alcohol eventually becomes so dirty that you have to do something. Given time, the polymer residue will settle to the bottom and you can easily pour off most of the clean liquid. You can also use filters with some success. But [Makers Mashup] had a different idea. Borrowing inspiration from water treatment plants, he found a chemical that will hasten the settling process. You can see a video of his process below.
The experimentation started with fish tank clarifier, which is — apparently — mostly alum. Alum’s been used to treat wastewater for a long time. Even the ancient Romans used it for that purpose in the first century. Alum causes coagulation and flocculation so that particles in the water wind up sinking to the bottom.