Magazine copies. For the gelli plate I made 2 batches of 1.5 cups cold water 3/4 cup glycerin 3/4 cup alcohol and 8 packets of gelatin then microwaved it and stored until it was clear the gelli plate came out really dense and thick. I spend like 25 bucks at Walmart for all the stuff and got like way to much so I can make I bigger plate if I want but I don’t think I ever will.

https://www.reddit.com/r/printmaking/comments/12hn2ke/help_best_diy_gelatin_plate_recipe/

I used 8oz vegetable glycerin, 8 envelopes of plain gelatin and 8 oz of hot water. Stir in the gelatin slowly and break up all clumps. Pour into a shallow container like a cookie sheet and let it set. If there are problems with the plate it can be remelted and reset.

ETA: my favorite source for tips is YeatesMakes on YouTube. Super creative guy who does a lot of different techniques, including image transfers with charcoal pencil, chalk pastel, and resists.