I've made a few crafts over the years with shrink plastic, but I'm too cheap to buy the stuff in the store, so I make my own. I collect #6 plastic from bakery and deli containers, wash it off and save it for projects. I've even used alcohol ink on shrink plastic before, but that time, I waited until after the plastic had shrunk to ink it. I had always been curious if you could ink it before shrinking--so I set out to find out!
I was especially excited when I took the lid off the container holding my twice baked potatoes from the grocery store. For one, I got to eat delicious potatoes with my supper, but I was doubly excited when I found that the lid of the container was #6 plastic...AND...they accidentally put two lids on the container! It's funny the things crafters get excited about. So I rinsed off the plastic and cut out the flat center of the lid. You can shrink the ruffled/fluted edges too, but it's much harder to decorate and to get it to look like an even shape--but it does shrink flat. After I cut the flat center square of the lid out, I punched a hole in the plastic with a regular hole punch. The plastic on the recycled stuff shrinks to about a quarter the size, so I punched my hole about a half an inch from the top.
Then I used alcohol ink and canned air to decorate the plastic. I squirted ink on and blew it around the plastic until I liked the design. You will have to hold down the plastic when blowing it with air, though, since the plastic is so light. So, you will probably get ink on your hands--wear gloves if this bothers you.
I repeated the process with my other square of plastic, this time with oranges, pinks, and purples. I was fairly happy with my plastic squares, so I turned on the oven to preheat to 350 degrees and lined a small cookie sheet with some foil (to keep any ink off the pan and just in case it sticks a little).
I put my plastic squares on the pan and put a brush on the pan to help with scale. These squares were about 3.5 by 5 inches before shrinking.
Once the oven had preheated, I put my plastic squares in for 2 minutes and then checked them. They had curled up, but that's fairly normal early in the heating process. So I put them in for another 2 minutes and they were still curled. And another two minutes...which is the longest I had ever kept shrink plastic in the oven, and they were still curled. So I pulled them out of the oven. They were hard in seconds and the ink was muddy and turning dark in places. It was a total fail. I knew I had never shrunk plastic with alcohol ink on it, but I had shrunk plastic with sharpie ink on it, and it had worked fine. Sharpie ink is pretty similar to alcohol ink, so I didn't think it would be this big of a fail. But it occurred to me that the ink may still have been a bit wet....which meant that one side of the plastic was cooler than the other and created the curl when shrinking.
So...fast forward a week to take two. I dug into my stash of saved #6 plastic and grabbed several squares that I could cut into pieces about the same sizes as the ones I had tried before. This time I also played around with the ink a bit by spreading it on with a foam brush--a technique I hadn't tried before, but that I will be using again in the future.
I set aside my pink inked plastic square to dry long enough that it wouldn't mix with ink that I dripped on top of it and I decided to go bold with some black ink. I dripped on the ink while dragging the tip across my plastic square. I waited a few seconds, and then I used the canned air to blow it around a bit. I was intentionally trying to be random, but it turned out sort of bird-like.
And just like on the first try, I decorated the rest by blowing ink around the square with the canned air until I liked the way it looked. After I finished inking 4 squares, I left them to dry--for real this time. I left them on my kitchen table while I watched TV for like an hour and a half. THEN I preheated the oven.
Just in case one of the contributing factors was that the ink side was facing up, I flipped the pink and orange one in the upper left over so that it was ink side down. Then I put them in the 350 degree oven for 2 minutes.
When I checked--they looked all curled up--but in different directions. I quickly closed the oven and started the timer again hoping things would straighten out this time.
After 4 minutes they were flat and I breathed a sigh of relief. The one that was ink side down was slightly smaller and muddled. Some of the ink transferred onto the tinfoil. So that one didn't quite work out. But, I learned that as long as you let the ink dry all the way, you can totally shrink plastic that has alcohol ink on it.
After the plastic cooled, I decided to seal my plastic squares with some aluminum foil tape. I've been using this tape to seal my glass gems decorated with alcohol ink lately. It is faster than using a spray or paint on sealer and has the added benefit of providing a shimmery background for the ink that makes it pop!
So I cut the tape to the size of the plastic square and pealed the paper backing off and stuck it on the side that I had decorated with the ink. Then I used a toothpick to poke a hole in the foil tape. I used some hemp cording to turn these squares into necklaces, but they'd make great key chains too.
So, if you're going to try alcohol ink on shrink plastic--recycled or store bought--be sure it's dry before trying to shrink!