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Paint remover


Nick_Karatzides
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While trying to build the JT-9T autogyro, I did not expect a sad & bad situation such as total failure on paint applying. Becasue some up to date unexplained reason (possibly old colours or bad white spirit solvent that I used), have led to drying crack. Unfortunately, I ignored all the warning signs such as thick grains left by the white colour in which I primed the scale model before the final painting. I was facing a possible total dissaster and months effort collapsing into few minutes. The problems appeared marked inside the red circles. Unfortunately, I have no photos of the model while looked completely written-off, because at that time I was not in a mood to take pictures!

 

I had no other better choice, than trying a full reset – after all, I had nothing to lose! The model was already FUBAR...!

 

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  • OPTION #1 - MODELSTRIP: This product, was the first thing came up as the most conventional solution to try paint removing. Following the instructions on the box, a generous stuff applied on the model, wrap it with airtight plastic bag to prevent drying and wait about 15 hours to let the chemical work. Opening the bag next day and checking the results, the colour (or rather the colour layers) were soft and could be removed by rubbing vigorously with an old toothbrush. Unfortunately, using the brush on some very delicate spots (even with careful use), had as result to break / or ruin a couple of plastic pieces. Moreover, the paint could not be removed through narrow points and difficult locations.

Result? FAIL! :(

 

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  • OPTION #2 - OVEN CLEANER: At this point and while I’ve already used all the ModelStrip material without being satisfied with the outcome, I decide to change tactics to something more unconventional, such as oven cleaner. Following the product’s directions as always, I sprayed the model with the material, wrap it with airtight plastic bag to prevent drying and wait about 15 hours to let the chemical work. Testing results next day, the oven cleaner failed no more than ModelStrip. I noticed that the colour could be removed but only when pressure and persistent rubbing with brush and that was prohibitive for some parts of the model.

Result? FAIL! :(

 

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  • OPTION #3 - SODIUM HYDROXIDE: Not having another solution, I approached the most unconventional method and visit a science specialist - my local grocery store!

- Hey man! I need something really strong to clean up kitchen’s oven?
- Really strong? Use this!


…and he gives me a dust covered 1lt plastic bottle found in an almost unreachable shelf. Reading the bottle’s label, I found out that it contains sodium hydroxide also known as lye (corrosive alkaline substance) or caustic soda and is a caustic metallic base. It is used in many industries, mostly as a strong chemical base with chemical type NaOH.


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- Are you sure that this will work? Are you sure that this is safe to use?
- Trust me. It’s gonna clean up the kitchen’s oven like a nuclear bomb!
- How much?
- 3.50 € . Take it or leave it.


Thinking about a possible failure, I filled a plastic bowl with the milky liquid contained in the bottle and threw all the model pieces inside. As long as the autogyro model was already FUBAR, I had nothing to loose to try. I sealed the bowl with a cover and leave the sodium hydroxide to act for 20-30 minutes while the instructions sets out to wipe the sodium hydroxide chemical liquid after 10 minutes. Opening the plastic bowl’s cover, a nice surprise followed. Styrene pieces simply and magically totally striped off the enamel colour layers! Absolutely success, without even apply brush cleaning! Amazing product - incredible grocer!

 

Result? THUMBS UP! :)


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Just because I couldn’t believe it and I wanted to make sure that the colour striped off because of the sodium hydroxide chemical (and not the previous used ModelStrip product or the kitchen oven cleaner), I decide to experiment. I threw into a bowl, already filled with the chemical, a 1/18 scale female figure that I was about to convert for a future project. The specific 1/18 scale female figure, is made by Fast Women brand and can be found by clicking HERE). The results after just 15 minutes in the sodium hydroxide chemical - Perfect! The following pictures, show the "before" and the "after".


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Keep in mind that the sodium hydroxide is (and thus should be considered) a strong caustic base. This means that:

  • Throughout the impregnation of the model parts into sodium hydroxide, you should take all the necessary protective measures (like mentioned in the warnings on the bottle’s label) and is certainly to use disposable surgical gloves made by latex and breathing mask with appropriate filters to protect against possible fumes.
  • The colour stripped plastic parts must be rinsed with soft acid to neutralize the caustic base and produce salt and water. Dunking the colour striped parts in plastic container filled with cooking vinegar and then rinsing with plenty of lukewarm water, plastic is now safe to handle with bare hands.

Under the above "adventure" circumstances and considering that all these years dealing with the scale modeling I've tried many color striping methods (including ModelStrip, kitchen oven cleaners, blue alcohol, brake fluid, nitro laquer disolvent, etc), I think that sodium hydroxide NaOH is (for me) the best method so far, for the following reasons:

  • Kitchen oven cleaners in spray canisters, may do the job, but they cost 3 - 4 € for a 300ml product in which also includes the propellant gas and you need to brush to remove the paint. On the other hand, the NaOH in liquid form is a pure substance, much less price, taking for 1lt bottle, which equals 3.3+ times more product! Using the liquid form NaOH (which you can fill a plastic bowl), you can sink several plastic pieces, same time!
  • The brake fluid may be effective and remove paint, but it is not plastic friendly plastic and is likely to convert the scale model into a blob of molten plastic. It is clearly more expensive and as far it is highly toxic, flammable and hardly to manege, I will not recommended it for scale modeling use.
  • Nitric acid laquer disolvent, could be a nice solution for metal figures paint striping, but it is not the best for the plastic. Just like the brake fluid, it does melt and damage plastic parts.
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Wow, that's absolutely amazing. That's the equivalent to the Isopropanol I use for acrylic. Amazon sells liquid Sodium hydroxide in 5 litre jugs but they're 50% concentrate. I'm sure that'll do the job but just a little longer.

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Wow, that's absolutely amazing. That's the equivalent to the Isopropanol I use for acrylic. Amazon sells liquid Sodium hydroxide in 5 litre jugs but they're 50% concentrate. I'm sure that'll do the job but just a little longer.

 

Yes, I'm sure 50% concetrate will also do the jiob. Use an old model for testing before trying the real thing, to check how fast & how strong it works. Also, I give you some results, from the test I tried so far.

 

ADVANTAGES of sodium hydroxide use:

  • Will strip ANY kind of paint! Acrylic, enamel, oil paint, you name it!
  • Will NOT effect glue joints (tested on models glued with CA superglue or Humbrol liquid glue),
  • Will NOT effect putty,
  • Will NOT resin parts,
  • Will NOT fog clear parts & canopies,
  • Will NOT effect plastic parts.

PS. Did not tried it yet on rubber parts.

 

DISADVANTAGES of sodium hydroxide use:

  • Since sodium hydroxide is corrosive alkaline substance, some special attention should be given on models containing photoetched parts because rust might build on PE & metal parts. This will happen after paint striped PE & metal parts exposure on air (oxygene). To avoid rust buil-up, wash the paint striped PE & metal parts with fresh flowing water to remove all NaOH after use.

Keep in mind that sodium hydroxide is (and thus should be considered) a strong caustic base. You should take all the necessary protective measures (like mentioned in the warnings on the bottle’s label) and is certainly to use disposable surgical gloves made by latex and breathing mask with appropriate filters to protect against possible fumes. Paint stripped plastic parts should be rinsed with soft acid to neutralize the caustic base and produce salt and water. Dunking the colour striped parts in plastic container filled with cooking vinegar and then rinsing with plenty of lukewarm water, plastic is now safe to handle with bare hands.

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Wow... that's great in-depth research. Thanks for sharing!

I use oven cleaner to totally clean up gun stocks. It pulls the dark grease right out of them.

For cleaning acrylic paint of a model I use car windshield fluid. By far not as strong as what you use,

but all I dared to use :)

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Thanks for this one Nick.

 

I work in a science-based job and use Sodium Hydroxide all the time (caustic soda), and I never thought of using it to strip paintwork. Your effort seems to show it works totally. Very impressive. I think I'll use this method in future.

 

Remember....try not to get this stuff in your eyes as the alkaline properties will attack the eye's chemistry quite badly.

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  • 3 months later...

I avoid all that..............I found a product a few years back that works GREAT, can be re-used several times, is relatively non-toxic, and will remove both paint and chrome plating.

It is called "Super Clean", and can be had from your local Auto Parts store (U.S.), for about 12 bucks a gallon. It comes in what I call a "People Eater" purple jug.

The only thing to watch with this stuff is that it will take the oil out of your skin just zap!!, so wear gloves.

You can soak plastic parts for several days with no damage to them, and depending on the paint, 24 hours is usually plenty.

I have NO EXPERIENCE WITH RESIN, so do your own experiments.

When done, strain and re-use........up to about four or five times (really haven't got it so dirty it wouldn't work, just got gross).

When done with it, pour down your drain (AFTER straining out all paint), it eats grease, so it's a "win-win".

 

This, like any chemical, can be HARMFUL IF MISUSED. Please read and follow label instructions. It is a grease emulsifier (parts cleaner), so use with caution and common sense.
 

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