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Stripping paint from die-cast metal

From this... To this!

The factory paint applied to die-cast metal products is generally durable. The finish can last for many years. The primary sources of damage are from impact chips, or wear for long-term contact to a specific area. On toys, however, this damage can occur at a more accelerated pace, due to wear and tear from play. I can tell you that mine sure took a beating.

This brings me to the topic of this article. At some point, the original finish is so damaged that touching up the flaws is no longer practical. It's best to just start over with a fresh paint job. Maybe what was one a 'toy' is now treated more as a 'collectable'. Or possibly the opposite hapenned. Restoration and rebuilding projects might warrant a clean finish, as well.

When I was younger, I tried filing, scraping, and sanding, at the original paint from cars that I wanted to repaint. The end result was usally a part with deep scratches, lost detail, and fragments of paint that looked worse than what I started with. A few years ago, I decided to try a chemical stripping gel ( FastStrip by Zinsser ) designed to remove paint from metals and other materials. I was so pleased with the results, that it is the only way I use to remove paint, regardless of the reason. It has never caused any damage to the metal, even on some parts that are over fifty years old.

These instruction show a step-by-step process for stripping paint and any other markings from die-cast metal. But first, a few words of...

Carefully Read and follow all warnings and precautions as listed on the container of stripping solution.

Eye and skin protection is strongly recommended.

Serious injuries can result if safety instructions are not followed correctly.

I hope these warnings have gotten your attention. I don't mean to scare anyone away from using this type of paint stripper. I just want to underscore the manufacturer's precautions for proper use and handling of it. I've had a couple of minor mishaps myself, over the years. While cleaning the solvent from parts, some has accidentaly come in contact with unprotected areas of my hands. The burning feeling started pretty quickly, but I was able to stop it by thoroughly rinsing the area with water. I don't even want to think of what would happen if I got it near my mouth, and especially my eyes. By following the safety instructions covered here, I hope to never find out.

I've divided the process up into the six steps, which are as follows:
  1. Get recommended supplies ready
  2. Place part to be stripped in container
  3. Pour stripping solution over parts
  4. Allow time for stripping solution to loosen and disolve paint
  5. Clean paint dissolved by stripping gel from part
  6. Inspect cleaned part, repeat steps 2 through 5, if necessary.

Step 1: Get recommended supplies ready

The picture below (click to enlarge) shows the supplies I recommend. Starting at the top center, and moving clockwise, these are explained in more detail as follows:
Click to enlarge
  1. The stripping gel. I use FastStrip by Zinsser most often. As of this writing, I pay around US$10.00 for a one quart (.946 L) can.
  2. A plastic containter to hold the part and stripping gel. I use an old margarine tub that has the recycle symbol along with a 5 and PP (see sample here) on the bottom.
  3. An old toothbrush. You could probably use any kind of small brush with nylon bristles and a plastic handle.
  4. Latex or rubber gloves. Exam gloves are OK, but I prefer the looser fitting kind that are probably more intended for household cleaning. There is no harm in reusing them, just as long as you discard them as soon as you notice any tears or holes. I don't recommend plastic gloves, like those used for food service. I've never tried them, but I suspect the stripping gel is strong enough to melt them. To your hands.
  5. Eye protection. Since you will be scrubbing parts with a brush, there is always the possibility that a small particle of the solvent could spray back a your face. Whether you use the style of goggles shown here, glasses with folding arms, or a full-face shield, just be sure you wear SOMETHING. Prescription eyeglasses a better than nothing, but be aware that contact with the stripping gel could damage special coatings those glasses may have.
And last, but not least, is the subject I will be using for the remainder of these intstructions, in the foreground.

Step 2: Place part to be stripped in container

Click to enlarge To the left (click to enlarge) is the part placed in the container used for stripping (see item 2 in step 1).

I always place my parts flat on the bottom of the container. As you can see, this one has been used several times. The only reason I can see to replace one is if a hole or crack develops, which could cause the solvent to leak. Any leftover solvent residue is easily removed by peeling it from the inside of the tub after it has dried, which ususally takes just a few days.

Step 3: Pour stripping solution over parts

Click to enlarge The picture on the left (click to enlarge) shows the stripping gel being poured onto the part.

I usually pour the solution over the highest point of the part, then let it flow around the sides. If an area looks like it hasn't gotten enough coverage, I use a an old toothbrush to move some solvent to it. There's no harm in completely submerging the part, but I haven't noticed that this speeds up the stripping process. It also uses up the stripping gel faster.

Step 4: Allow time for stripping solution to loosen and disolve paint

Click to enlarge Ten minutes after the part was soaking in the stripping gel, the picture on the left (click to enlarge) was taken to show how fast it starts to work.

Notice the distortion in the paint pattern in this picture as opposed to the previous step. Some is due to the stripping gel itself, but the majority is because the paint has softened that much. Some paint is more stubborn that the example shown here. I usually let a part soak 6-24 hours between before cleaning it.

Step 5: Clean paint dissolved by stripping gel from part

Click to enlarge The picture on the left (click to enlarge) shows how easily the softened paint can be removed with a toothbrush.

If you haven't done so already, now is the time to put on the skin and eye protection that was mentioned earlier. I usually brush off as much paint as possible, then thoughoughly scrub the part unter running water.

Step 6: Inspect cleaned part, repeat steps 2 through 5, if necessary.

Pictures of part after first cycle of cleaning (click to enlarge)

Front 3/4, after stripping and cleaning Rear 3/4, after stripping and cleaning Bottom, after stripping and cleaning

After you have thouroughly cleaned the part, examine it to see of another cycle of stripping is necessary. If you look closely at the above pictures, you'll see bits of paint left behind after the first cleaning. Many of these are removed through sanding when I'm preparing the part for painting. Others can be chipped or scraped with a hobby knife. I don't concern myself much with leftover paint on the underside of the body, as this is an area that is seldom seen on a completed project. There is no harm in repeating the stipping and cleaning cycle to remove all traces of paint, but it may not be worth the time and effort, if the remainder can be removed in the ways I juist mentioned.

So, there you have it. This is what I have found to be the fastest, easiest, and safest (for the part, anyway) method of stripping die-cast parts down to clean metal. I've been following it for several years now, and I'm sure that you will have the same success that I've had. If you have any reservations, just practice on a spare or scrap body. If you're like me, you have plenty of these lying around. When you fell comfortable enough, try it on an actual project. And when you do...

 "Happy Stripping!!"

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