Thursday, January 31, 2019

Salt and Pepper and Removing Paint


Here is a project that will take a couple of blogs to finish.  I will begin with how to remove paint from plastic baby bottles (party favors).  Then in the next blog I will tell how to make the grinders.

I thought these baby bottles from Hobby Lobby looked just like salt and pepper grinders.  Problem was the pink paint!  I had to make 100 sets for an event (that’s 200 total!) so I needed a way to remove the paint.

I probably wouldn’t have taken the time to research paint removal for just one pair but since I had to make so many it was worth the time.  I am documenting what I learned in hopes of saving someone else the research time.

I should start by saying that there are many different kinds of plastic and many different kinds of paint.  I don’t know what kind of paint they use on these favors but it must be some kind of spray enamel.  It is very hard to remove.  I wanted the bottles to be crystal clear.

My goal was to find something that would take the paint off without fogging or etching the plastic.  Even though I am a Chemist by training, I mostly relied on trial and error (not being familiar with the paint industry).  I read lots of blogs on car modeling, plane modeling, etc. and tried many products.  You can see from the photos all the things I tried:

Some things frosted the plastic.  Other things either didn’t dissolve the paint or took too long (meaning I gave up not wanting to wait more than a full day to see if it worked).  Here is a summary of what I tried.

These products did nothing even after soaking:
  • Simple Green (full strength)
  • Paint Thinner (kind of worked but would have to be scraped)
  • Alcohol (70% Isopropyl)
  • Testors Brush Cleaner
These products etched the plastic:
  • Zip Strip paint remover (it DID remove paint too)
  • Nail Polish Remover (non-acetone)
  • Nail Polish Remover (acetone) -
  • Model Master “Acryl” Dried Paint Solvent
Winners! These both worked removing paint with no fogging but required soaking overnight:
  • Brake Fluid
  • Easy Off Oven Cleaner (requires some scraping) 

A couple of notes:
  1. All of these are solvents and require use of gloves (and maybe goggles!) and should be used only in well ventilated areas (like the garage with door open).
  2. Since I was doing this for 200 bottles, I did it in batches.  I put 20 or 30 into a plastic bag and set the bag down into a disposable drink cup.  I poured the brake fluid into the bag and sealed it up and let it soak overnight.  It was kind of messy. 
  3. The next day I drained off the used fluid (the pink-ish stuff in the baggie in the photo above).  Then I used paper towels to wipe off the fluid.  There was a pink film still on them so I gave them another quick rinse in clean fluid and swabbed the pink out of the inside of the bottles with a Q-tip.
  4. Disposal - I was left with the problem of what to do with the used brake fluid.  It can’t be poured down the drain.  I drained it off the bottles after they soaked and poured it all back into a plastic container.  Thanks to O’Reilly Auto Parts I was able to take the used solvent back to the store and they disposed of it.  You might have to ask around.  One other auto parts store I bought some from would not accept it.
  5. It takes a little scrubbing to remove all bits of the paint.  I had to sand the center tops of some of the bottles after clipping off the nipples. 
  6. There is one more trick I learned to solve the problem of fogged or scratched plastic.   Some of the car modelers coat the fogged plastic with Pledge Floor Care (Wal Mart) (I think this used to be called “Future” floor polish some years ago).  This helped where the tops were sanded to make them clearer.  Car modelers use it for scratched windshields. (you see I have marked my bottle "Minis" because I am likely to forget why I bought it and might throw it out!!)
 That’s all for this blog.  Hope this was helpful to someone.  I know I am indebted to all those car and boat modelers who took the time to blog about their paint removal problems!  Next time how to make the grinders!