Stripping Paint From Metal and Plastic Parts

It is nice to work with brand new pristine parts but many times it is cheaper or necessary to start with used ones. This means I have to strip paint off of items that some paint monkey (which is often me) has gobbed multiple coats onto. It has been a steep grading curve as my inner paint monkey is a slow learner.

I have used commercial stripping products such as furniture varnish remover, automotive paint stripper, naval jelly and brake fluid. They are all caustic with strong odors and very messy to clean up. Sometimes they attack the item being cleaned and ruin it. I want to find a clean, effective method that does not poison the environment or destroy my plumbing. After doing a lot of research I am going to experiment with some less toxic products. Let me state right now I am not the originator of any of these ideas.

For the purpose of this experimentation I will be using items made from pewter, brass, pot-metal and injection molded polystyrene plastic. They are all covered in a variety of paint types including latex house paint, acrylic enamel, oil based enamel, spray paint and lacquer. Some have parts glued together using hot glue, PVA, Cyanoacrylate, MEK or other hobby glues.  Few of them are railroad items, they are just test subjects so don’t get hung up on them belonging to another hobby class.

The Crock-pot Method

A few weeks ago while channel flipping I caught part of an episode of “This Old House”. They were showing how they stripped decades old paint layers off of doorknobs, hinges and cabinet hardware by cooking them in a crock-pot full of water. Some scrubbing, and scraping that would not be possible small model items was required but I wondered if I could find a way to use this on my hobby stuff.

WARNING: Do not boil solvents or cleaners in a crock-pot. You will fill the building with gasses and odors at harmful levels.

I pulled out a selection of plastic and metal war-games figures and a pair of metal and plastic Hubley car parts. I did not paint any of these items but I can tell from looking at them that every kind of hobby paint is represented on every type of material. I have had these items for years in the “someday box” so I know the paint is old and dry. Here is a before pic of the lot.


First I bought an old one gallon crock-pot at the thrift store for $5. It is the kind with a simple rotary switch and no timer. New ones automatically turn off after a maximum of ten hours so this style is essential for the long cook times. You are not going to want to eat food out of it after this so do not use your $45 Hamilton Beach cooker with computer controls. I decided to start as basic as possible putting everything in just as you see it. The figures are all metal with plastic bases. Some also have plastic arms. The figure center bottom is a plastic body with metal arms. The cars all metal except for the rumble-seat cushion which is plastic. The crock-pot was filled with water and set on high. I ran it for 24 hours.

I got a mixed bag of results. The figure bases all curled and melted becoming very brittle. They were ruined as was the rumble seat cushion in the roadster body. The plastic arms and body parts on the figures held up just fine. I was pleased that most of the glue (all types) had softened and either dissolved away or was so soft I easily pulled the figures apart without any damage. The sole exception was the plastic to plastic joints that used superglue.

Some of the paint dissolved and the items were left completely clean or close to it. On some figures the paint remained very hard and firmly attached. On other figures the paint had de-bonded from the surface but otherwise remained very durable. It came off like skin.

Here are the items after a 24 hour cycle. All items were scrubbed with a soft bristle toothbrush under a thin stream of running water. Total time to scrub everything was about 30 minutes. These figures were the most successful. Most of them only had primer or a single coat of acrylic enamel water based paint. The top center figure was the exception. It was primed, painted and sealed but still came clean very easily.


This group of figures were also primed, painted and sealed but almost none of their paint came free. I did notice that the toothbrush was useless. The bare metal is the result of me dragging a fingernail across the parts. Where the brush would not move it, the paint here sloughed off in sheets.


These are plastic parts. The bodies are solid plastic and held up fine. The paint coming off easily but leaving a slight haze. The bases melted and had to be cut off. Fortunately I have new ones by the sack full.


Now this is the confounding part. These two figures came from the same source and were painted in the same manner. You can see them next to each other in the first picture above. They responded very different to the process. One came almost completely clean while the other is still fully coated.


Along the same lines are the two car bodies. You can see the rumble seat piece melted and was ruined. The roadster paint is mostly gone with gentle scrubbing but still has some hard patches that only come off when scraped with a plastic putty knife. The paint on the Victoria was almost all gone when I removed if from the pot, what was left literally wiped off. I have seen this sort of thing before when using Pine Oil as a solvent and suspect the roadster was painted with old spray lacquer while the Vitoria was painted with one heavy coat of low quality spray enamel. Neither car shows any evidence of a primer coat being used.


I decided to run everything that was still holding paint through a second time. The process was repeated with very little change. I even bought a firm toothbrush and while it did a markedly better job of pulling the paint off there was still no real improvement on some of the figures. A few figures remained very resistant to the process but I could tell their paint was softening. Back to the crock-pot for another round. Along with the hold outs I added a group of new figures and am now cooking them all for 48 hours. This is what TOH had originally stated to do but I thought the small figures and thin metal car bodies would not need that long.

Here is what I know so far:

  1. The crock-pot and water is very user friendly with no fumes or toxic chemicals involved.
  2. Fill the crock-pot to within 1″ of the top and check it every 10-12 hours to make sure items are not above the water line. It will boil off a lot of water.
  3. The success rate is about %80.
  4. A long cooking time is needed, 48+ hours.
  5. Type of paint is not that important since the heating process breaks the bonding to the surface rather than dissolving the paint layer.
  6. Thickness of the paint coat seems to be the most decisive factor.
  7. Only thick plastic parts can survive the process.

More to come….


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