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Stripping paint with isopropyl alcohol


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#1
The Observer

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Hey guys, quick question: I have heard that one can strip plastic and resin very safely and reliably with isopropy alcohol. Now, locally, I have 70% and 99% isopropyl alcohol available - is there any difference/danger between the two in regards to my minis? Any tips on working with the stuff?


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#2
Beaky Brigade

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Hi there,

Quick disclaimer, I'm not a chemist or material scientist, I'm only advising you based on my own research and practice with the stuff.

Lets get the safety information out the way first:

Pure alcohol is flammable, don't work near fire or sources of ignition!

It's bad for your health if you inhale it or let a lot of it get absorbed through your skin. You may or may not drink 'normal' alcohol for leisure, and perhaps getting fume drunk while stripping minis sounds funny, but absorbing this into your system can damage your liver. Now it's not hydrochloric acid of course, but it's worth protecting your health.

I recommend rubber gloves (normal washing up gloves are probably fine) and a respirator rated for vapours, I.E one you would use for working with spray paints. Not a cheapo dust mask! Also work in a well ventilated area, open a window etc.

You'll need to soak the minis for at least a few hours, and an air tight container is necessary for this. A re purposed jar or cheap tuppurware will suffice.

Now some some people might argue this is overkill for stripping a few minis, but it's up to you how much you value your health and safety.

 

Scary stuff aside, the actual applications for stripping minis...


I've found this is the most effective practical paint stripper. All the other solutions involve using various cleaning products that may not be available internationally which have various downsides such as damaging your glue or minis and leaving a nasty smell or residue.

 

With isopropyl you're getting 100% good stuff. Now I have heard that isopropyl can soften resin minis, I haven't tried it myself. It probably depends how long you let it soak but I would be cautious before dipping a titan in. If you do want to try it maybe use an unwanted model first.

 

 

I can't write a complete guide at the moment but my main tips are:
 

  • 99% is a good concentration to use if possible. Lower concentrations may work but more slowly
     
  • Required soaking time will vary based on the type of undercoat, varnish and the age of the paint
     
  • I wouldn't leave anything soaking longer than required to strip it. Have a plan for when you are going to remove the minis rather than leaving them for a few weeks. I haven't ruined anything like this but better to be safe
     
  • All stripping requires some work. I would suggest letting the models soak for a few hours, doing an initial tooth brush to loosen things, then a further soak to finish it off
     
  • You don't need to fill the whole container, if you fill it to half submerge your mins you can turn them half way through the procedure, saving alcohol
     
  • You can reuse the same alcohol indefinitely, just run it through a coffee filter to get the big chunks of paint out. It won't turn completely clear but will still be a pretty high concentration and can be used again. I would keep it in a different bottle to your fresh stuff
     
  • If you have an electric toothbrush consider using it with an old brush head to aid stripping. I would wrap the wrest of the brush in something to protect it from splatter
     
  • If you have an ultrasonic cleaner you can use this (filled with water!) as clean up stage. I wouldn't use alcohol with a cleaner as it might heat the alcohol and will vaporise some of it. It's helpful, but not required.
     
  • Pipe cleaners/airbrush cleaning brushes are really useful for scrubbing in crannies
     
  • The minis will never look sprue new, but hopefully you can get them to a stage where it's impossible to tell they were stripped when repainted

 

Hope that helps!


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#3
Laughingman

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yes you can, I prefer  99% isopropyl alcohol. 70% appears to be less effective in my experience. I've even stripped an entire vindicator with thick automotive primer this way.



#4
Arkhanist

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I prefer biostrip 20, a non-flammable, non-toxic virtually odourless paint stripper that strips minis significantly quicker - but as a UK product it's not always easy to get internationally and is more expensive.

 

IPA does work OK, I mainly use it now to deep clean my airbrush as needed to get small amounts of dried paint out of awkward spots (teflon seals can cope with it, rubber ones, less so)

 

Don't use IPA straight in a consumer-grade ultrasonic cleaner; in small quantities you'll probably get away with it, but it does have a very low flashpoint and nobody wants a fire! They use IPA for industrial degreasing in ultrasonics, but those are properly sealed machines. Much safer to put the IPA and minis in a closed plastic or glass container and put that in water if using an ultrasonic.

 

I've found 70% IPA doesn't shift paint that well, though it does weaken it. 99% is much better, so go with that one.

 

Although it's mostly safe in small quantities (70% IPA is the main ingredient of many antiseptic hand gels) gloves is still a good idea when you're soaking your hands in 99%, and work in a well ventilated room. (don't drink it, obviously)

 

Other than that, what Beaky Brigade said! Especially about giving it several rounds of cleaning, IPA will usually require at least 2 rounds of soak then scrub. I have an old electric toothbrush that saves on some manual effort. Never had IPA affect plastic models, but avoid with resin parts, some types of resin can be permanently damaged.

 

Though if you absolutely need to clean resin models with IPA, definitely test first with a scrap piece of the same type; you can get away with it with some resins with scrubbing with IPA (rather than soaking). But, for example, forgeworld resin will go so soft you can indent it with a fingernail.


Edited by Arkhanist, 04 February 2020 - 10:58 PM.

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#5
Fajita Fan

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I had models sitting for months in Simple Green that weren’t coming clean who where down to bare plastic after an hour in 91% alcohol. Good stuff.

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#6
Axineton

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The flashpoint of isopropyl alcohol is around 11-13 degrees Celsius so if your going to use it just make sure there’s no sources of ignition around. Boiling point is a different matter. It’s around 82-83 degrees. 
 

50-70% isopropyl alcohol is used in your hand rubs in hospitals and doctors surgeries etc anywhere where cleanliness is around but as you go past the 70% barrier it gets more toxic and irritating so wear decent gloves when handling it. 
 

It’s great for stripping minis mate but like others have said just take care and also ventilation is a good thing too. 


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#7
The Observer

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Thanks a bunch for all the helpful recommendations and safety tips!! :D
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#8
Gederas

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Regarding resin miniatures and isopropyl alcohol: It only becomes an issue with melting if you forget them in the iso for a while.

 

Plastic miniatures?

I left mine soaking in a mix of isopropyl alcohol and Super Green (that green de-greaser that seems to have thirty different names :lol:) for about a month and they were fine. It stripped the models down to the bare plastic, not just the primer.



#9
Wakkomaster

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Well, so far I've used quite a number of "things" to strip my miniatures. My latest attempt was with Isopropyl Alcohol and I can confirm what's been said so far: doesn't harm plastic, it *does* its job but requires a lot of scrubbing, it smells awfully and you don't want your skin get in touch with it for too long.

My results were a bit underwhelming though. One of the problems I found with I.A. and other detergents made from it is that they do soften up the paint, which will be goopy and scratchable after you left it soak for a while (for 99% I.A. you should be good to go overnight, with I.A. based floor washes and detergents it will take a few days); however the moment you rinse the miniature with water the paint will harden again, which means multiple baths are needed. Removing the paint from the recesses usually requires a toothpick and a lot of patience.
However I can confirm everything Beaky Brigate wrote up above.

I tried Biostrip some time ago and whoa, that's on totally another level. It's far more expensive the I.A. and it's "consumed" in the stripping process, it's not re-useable like I.A., but it's quick and extremely effective as it really melts acrylic paint. It's not a liquid, more of a paste so the way I use it is to dunk the miniature in the Biostrip, shake it a little to remove the excess and place it in a small plastic bag. It has a weird smell (at least my batch did), a bit of almond and fruits with a chemical "aftertaste", but I didn't find it as awful as I.A.. Still, use gloves and handle with care. After a couple hours you should already see the paint melting, and as long as the dried paint is in contact with Biostrip it will do its job - in other words, brushing the miniature with a toothbrush after a few hours and placing it back in the bag should do the trick. Unfortunately the paste used is gone for good, as the paint can't be filtered out and you'll end up with an oddly coloured paste stuffed with dried paint… but as I said you'll end up with almost pristine miniatures in two or even just one bath.


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#10
Arkhanist

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T

 

 

I tried Biostrip some time ago and whoa, that's on totally another level. It's far more expensive the I.A. and it's "consumed" in the stripping process, it's not re-useable like I.A., but it's quick and extremely effective as it really melts acrylic paint. It's not a liquid, more of a paste so the way I use it is to dunk the miniature in the Biostrip, shake it a little to remove the excess and place it in a small plastic bag. It has a weird smell (at least my batch did), a bit of almond and fruits with a chemical "aftertaste", but I didn't find it as awful as I.A.. Still, use gloves and handle with care. After a couple hours you should already see the paint melting, and as long as the dried paint is in contact with Biostrip it will do its job - in other words, brushing the miniature with a toothbrush after a few hours and placing it back in the bag should do the trick. Unfortunately the paste used is gone for good, as the paint can't be filtered out and you'll end up with an oddly coloured paste stuffed with dried paint… but as I said you'll end up with almost pristine miniatures in two or even just one bath.

 

Biostrip does go a funny colour after use, but still works fairly well for fresh minis. Some people just leave minis to soak in the biostrip pot itself, and let the gunk accumulate, yet it continues to work fine. I do like you though; dip minis and leave them in a spare tupperware for a few hours and just wash away the leftover goop.

 

My current pot has started to thin with about 1/4 left given it's over 3 years old now - it's more like pouring cream, but still works well. Will definitely be buying more; it's expensive in comparison, but £5 for dozens of minis (enough to last for years!) is still within budget for me, and it does save a lot of scrubbing.

 

It definitely does smell of almonds, doesn't it? But not very strongly, to me anyway. I do use a glove when dipping models into the pot, but it's supposedly non-toxic and non-irritating and have had no issues using it with my bare hands when scrubbing/rinsing models under the tap.


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#11
Axineton

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I’ve also used biostrip in the past and it is great stuff I just hate the goopyness of it. Yeah definitely non toxic but it will cause defatting of your skin. It’s harmless enough so much as it doesn’t have a UN number for shipping and no special warnings on the safety data sheet here: https://www.restexpr...rip_20_COSH.pdf


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'Show me one who mocks the Harlequins as Clowns, and I shall show you a corpse in the making'

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#12
Firedrake Cordova

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Dunno if it helps, but I've used Winsor & Newton Brush Cleaner, and Vallejo Airbrush Cleaner to strip plastic models (without issues) - it's a case of putting the mini in the liquid for a couple of minutes, scrubbing with an old toothbrush, and repeating until clean (keep and re-use the liquid, when finished).  From the MSDS, W&N Brush Cleaner appears to be mostly ethanol.  I believe Vallejo AB Cleaner is also alcohol-based (IPA/ethanol, I think) (with some lubricant).


Edited by Firedrake Cordova, 08 February 2020 - 11:53 AM.

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#13
Djangomatic82

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I've been using Iso 91% to strip models since i've started. You dont really need to let it soak in the alcohol if it is a larger piece or something you can scrub with an old toothbrush without fear of bending or breaking something. The last time i stripped a few rhinos and razerbacks, i just had a pippette full of iso, squirt a bit over an area , give it about 3-5 seconds,  then scrub it with the tooth brush under running water in the sink. after about 5-10 seconds, i'd move onto the next spot. Like this i was able to clean a rhino in under 10 minutes. Corners and crevasses are always a pain, but a tooth pick or some other soft-ish pointy thing to dig out the corners is all you need. I'd also not worry too much about fumes. I use the same iso to clean my airbrush between colors and its not really an issue, just be prepared for pain if you have any cuts or scrapes on your hands if you get it in there. it really is the only no fuss no muss method of stripping stuff.


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#14
Axineton

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I'd also not worry too much about fumes. 

Ok then but here’s a safety data sheet from a generic 91% isopropyl alcohol product. https://www.hydroxla...91%-1-09-18.pdf

 

pay particular attention to section 4.2 and section 11. It’s not the most hazardous product out there but it’s still nasty if you don’t treat it with a bit of respect mate. 

 

Anyway OP just obviously use your common sense and I’m sure you’ll be stripping models like a pro 


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'Show me one who mocks the Harlequins as Clowns, and I shall show you a corpse in the making'

- Autarch Antelyth Thyllian Of Craftworld Saim-Hann.


#15
Djangomatic82

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I'd also not worry too much about fumes. 

Ok then but here’s a safety data sheet from a generic 91% isopropyl alcohol product. https://www.hydroxla...91%-1-09-18.pdf

 

pay particular attention to section 4.2 and section 11. It’s not the most hazardous product out there but it’s still nasty if you don’t treat it with a bit of respect mate. 

 

Anyway OP just obviously use your common sense and I’m sure you’ll be stripping models like a pro 

 

ok, the general take away is, Dont huff it, dont drink it, dont get it into your eyes and dont light it on fire. but considering that we literally pour it into open, bleeding wounds, baring those mentioned situations, its not that bad and common sense should prevent most issues. I'd be much more worried about the propellants in spray cans or the additives we put into our paint.


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#16
Axineton

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Oh yeah they’re definitely  a different story mate 


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#17
The Observer

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Okay so I have done some conclusive testing:

 

For plastic, primed, painted and then varnished minis, I have found that if left in ISPA for 24-36 hours, the paint will slide right off. However, the crucial bit here is to not hold it under a running faucet while scrubbing the paint off - if necessary, wetten your brush with the ISPA and scrub the mini. Once all paint is dislodged, run it through some water.

 

For resin - treated in much the same way - the same rules apply, however, don't leave them in for longer than 4-5 hours as then they starten to soften up.


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#18
Isolia

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So from a chemist point of view :

IPA, Isopropyl alcohol, is a fire hazard as stated before, so avoid heat sources and especially open flames. And as all volatile alcohols, you need a well ventilated workspace to avoid dizziness from the vapours - the boiling point may be relatively high but its vapour pressure makes it quite volatile.
It is relatively harmless through skin contact, but wear gloves - it dries your skin, some can be more sensitive than others, and it has some penetration, which means it may help other stuff get in (from your paints, mostly). And if you have microcuts on your skin you'll feel the reason why gloves would've been a good idea :D
So wear gloves (nitrile is fine for shorter times, thicker butyl or neoprene are better for prolonged work), and ventilate the area well.
A surgical/paper/particle mask is funny but useless for organic fumes unless you have a respirator with an active cartridge, so open a window and be near it :)
If it gets in your eyes somehow, rinse out with water. If your eyes are Goblin Green afterwards, go see a Painboy ;)

Now that the safety part is covered, I had great success with 70% IPA, about an hour soaking, and a toothbrush and some elbow grease ;) The higher grade stuff is a bit more annoying to work with in terms of fumes and eats the thinner nitrile gloves quicker (they soften and tear eventually).
Note that I never had any issues on resin either. As stated font soak minis too long as the material itself may be resistant but the solvent may remove plasticisers, addives etc which can render the mini softer or brittle.


You want to avoid doing this in the sink because
1) you'll put pollutants down the drain (IPA and the pigments) and
2) pigments love to stick to ceramic /enamel sinks.
Do it in a bucket or dedicated (IPA resistant) container, let the IPA vent off outdoors, and wipe clean, dispose of wipes in the bin.
If it can't be helped, dilute with plenty of water before disposing in the drain, but do avoid that.
If you have a sceptic tank (some homes not connected to general sewage) you are in for a ride if you throw a powerful antibacterial down the drain :D
In larger quantities, you can collect the solvent waste and bring it to your local waste disposal facility labelled as dangerous waste, they know how to handle it.
Hope this helps, most of it was covered before but I wanted to share my postlitive experience with IPA for stripping minis.

Edited by Isolia, 14 February 2020 - 07:29 AM.

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#19
Fajita Fan

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Update: 91% alcohol annihilates contrast paints on contact. I'm going to do a little experiment on my AT knights that I'm stripping (I don't love how they look) with diluted alcohol because I may be able to save the silver primer underneath if I just use q-tips instead of soaking.  As I poured alcohol into a cup with minis in there the contrast paint disappeared on contact.  It'd be really cool to be able to save the primer layer from needing to be fully stripped and resprayed if possible.   


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#20
Fajita Fan

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Update to the update: 
Due to people buying up rubbing alcohol to freebase their hand sanitizer all my local stores are sold out.  This coronavirus has finally hit home.  dry.png


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#21
Caius_Karayan

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Just wanted to chime in here and say that while I have success in removing the paint using srugical spirit from Boots (UK) and other 99% branded alcohol I then have problems when It comes to repainting the model (especially with the blue easy to build miniatures and less so with the standard grey plastic miniature).  I dont soak the miniatures, I will always use a q tip or old toothbrush to gentle scrub/remove the paint. 

 

The effect it leaves is a kind of a patchy gloss finnish where the paint doesnt seem to adhere to the plastic correctly.  Spray primer sticks fine but the next coat of layer paint will have the same effect.  I have changed brushes/water/pallettes and paints as I suspected something had been contaminated but the problem still remain.  If i can get a good picture of it I will post it.  If anyone else has had a similar issue and has found how to fix it that would be great!

 

As others have mentioned I highly recommend biostrip20.  I have used that for a very long time and had no issues.


Edited by Caius_Karayan, 04 April 2020 - 08:33 PM.





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