I accidentally removed some paint from my child's toy with surgical spirits while disinfecting it, what went wrong?

Question

So during the coronavirus pandemic I have been spraying any package contents I receive with 80% surgical spirit if it is plastic and nonedible.

Today my daughter received a couple of new toys in the mail, and I sprayed them as I usually do. One was plastic, the other was wood, and I honestly didn't even think this would be a bad idea. Now I know better.

Fortunately I realised what was going on pretty quickly when I picked a piece up and it was suddenly very tacky. I separated out the pieces and set them out to dry.

I understand a bit of woodworking and have done some in the past. I understand that the alcohol must have been a solvent for the toy paint. However I'd like to understand better what happened in order to avoid this happening in the future.

Particularly I'd like to understand:

• What kind of paint this is that this happens to (or a family of paints, or even all paints)? Is this common among paints?
• Is this method appropriate for some paints, or just a big no-no in general.
• Is it safe to use simple soap and water on this toy instead (or the wood bits of it)? (I would be concerned about the paint being a water based paint and coming off, or the wood reacting to the water in some way).

Other things I just realised:

• I'm using 'paint' indiscriminately here to mean the layer(s) of stuff on the wood, but it could be a finish or varnish or another word I don't know.
• There could have been another finish on the toy, but I don't think so because the paint colour came off on my fingers.

(I'm trying to avoid the probably offtopic question of "how do I disinfect a wooden toy from the coronavirus" because this is a woodworking site, not a medical one but I would like to understand better what went wrong so I can clean wooden toys properly in the future.)

Answer 1

Alcohol is a strong solvent, and full-strength it'll damage almost any commonly found finish to some degree, even so-called water-based finishes. Left long enough it can even damage the wood underneath (though this is an extreme case.)

Toys are often finished with acrylic paint, as these are usually the types allowed by the manfucturers for items intended to be gnawed on by babies. Acrylic paint is soluble in alcohol. But even "latex" formulations can soften with strong alcohol. Obviously, varnishes intended to be mixed with alcohol will also be damaged if sprayed with alcohol later.

There are some enamels that, once cured, will not be affected to any noticeable degree by alcohol.

To answer your hidden question, use soapy water to clean and disinfect items. Soapy water is very effective at destroying the fatty acids surrounding viruses, which destroys them completely. You don't need fancy disinfectants. Just get a spray bottle and some concentrated all-purpose surface cleaner from the hardware store. Mix it with water to the recommended concentration on the label. Spray, wipe clean, let dry.

Answer 2

What kind of paint this is that this happens to (or a family of paints, or even all paints)? Is this common among paints?

Although it's not the only possibility this would be common to the great majority of waterbased paints¹.

No other common paint formulations (in the West at least) would be readily soluble in an alcohol.... the other coloured coatings that might be used on something like this include all oil-based paints (which includes all true enamels), or a solvent/resin formulation as with coloured lacquers of various types, which aren't really affected by alcohol.

As you used an 80% spirit the remaining 20% is primarily water, so there is a small chance the paint is water-soluble but I think this unlikely. A quick test with plain water will show whether it is or not.

Note that as this is surgical spirit, and not just "80% isopropyl alcohol" for example, there are likely to be other ingredients. In the UK the primary one may be methyl salicylate, but it's present at such a low level that I think it's unlikely to have any significant solvent effect even if it were a solvent for dried paint².

Is it safe to use simple soap and water on this toy instead (or the wood bits of it)?

Safe, very likely yes. Effective, not so much. Soap doesn't directly kill microbes, it aids in the removal of contaminants from the skin because of its detergent action, with the mechanical rubbing/scrubbing having the main effect. So to be effective at truly decontaminating a surface like this cleaning with soapy water would need to be prolonged and involve brushing/scrubbing, which obviously isn't viable and would soon lead to the paint being damaged.

(I would be concerned about the paint being a water based paint and coming off

Waterbased paints are almost all insoluble in their original solvent/carrier, if they weren't they'd be at risk of just being dissolved by sweaty skin for example.

Waterbased paints (and varnishes incidentally) are nearly invariably based on an acrylic of some kind..... including so-called latex paint in the US, which doesn't have a latex base as the name might suggest. Almost all wall paints and many gloss trim paints and 'enamels' that feature water cleanup, are an acrylic of some kind with or without some additional modifiers to increase wear resistance, waterproofing and other characteristics.

or the wood reacting to the water in some way).

Despite being painted the wood can still react to water to a degree because the majority of waterbased paints are porous. Hence why waterbased exterior paints may be referred to as "breathable", since they allow water vapour to pass through so that the wood underneath can't get waterlogged as can happen with e.g. the alkyd paints that preceded them for this purpose.

Brief exposure to water shouldn't have a harmful effect on the wood however, but prolonged exposure can so is best avoided.

Off-topic but anyway
As a closing comment, common household bleach in solution with water is more effective, and lots cheaper, as an all-round surface disinfectant than alcohols. And note there's a marked difference in effectiveness of ethyl alcohol (ethanol) versus isopropyl alcohol or methanol.

NCBI page, Use of disinfectants: alcohol and bleach.
CDC source, Chemical Disinfectants.

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¹ What we call waterbased paints are emulsions (more accurately suspensions) in water of microscopic particles of something that isn't actually water soluble.

² Even a very much stronger solvent than any alcohol is far less effective when heavily diluted with water. Acetone for example when diluted with water, as in some nail-polish removers, has a noticeably reduced solvent action compared to pure acetone.