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Hi, im getting back into the saddle after some time away and since my Air Brush is out of commision for the foreseeable future, i am forced to do blending and layering by hand (something i detest).

So as a little hack i was wondering if i could use something like a 50-50 Isopropyl alcohol to water solution to thin down say vallejo paints (or any other water based acrylics for that matter) to get a rapidly evaporating(drying) transparent paint.

Would that thinned down paint, eat at previous layers?.

I know Isopropyl alcohol is used as a thinner for airbrush paints, but i dont know if it is a real thinner (as in it breaks down the paint) or it is the fact that it is water soluble and of rapid evaporation.

Isopropyl will strip acrylic paint. It will weaken the paint surface that you apply it to, and whilst I've never tried what you are asking, I have used isopropyl expressly to strip paint.

You get away with isopropyl in airbrush thinners because you are laying down very thin coats and you aren't agitating the surface of the paint. In ordinary painting, the kind of brushstrokes you make I think could easily break apart the previous paint layer is you were using isopropyl as a thinner.

To my understanding, isopropyl is used as a surfactant - not a thinner. i.e. it's an additive that reductes the surface tension of the water (in the same way as many flow improvers, or dish soap can do) to allow it to flow more freely. This makes it a useful additive to let it flow through your airbrush cleanly without it clogging, but again, I don't think its primary purpose is to actually thin the paint.

A technique I have heard people use is to mist a model with a light spray of isopropyl, and apply a wash or speckling to the wet mini (again using its properties as a surfactant to make the acrylic flow more). Another example of something that doesn't really agitate the surface of the previous paint layers.


So.... Probably not a good idea? I haven't tried it but from what I know and have used it for I would say it's not a good idea.

I used to break down old acrylic and oil paint from brushes I forgot to clean the night before using overnight soak in Isopropyl at 70% or higher.
It does break down paint, but not too aggressive. If you are brushing it on, the brush might scrape old layers right off.

You can dilute Isopropyl with water, estimate 50% or lower, and give it a try, it should be ok, BIG emphasis on "should". I mean, it is not acetone right?.

I am sorry I just saw this ( Isopropyl alcohol as water based acrylic thinner?) and could not help me self, even though that is not what you are talking about:
Yo dawg, water aint thin enough?! add a thinner to your thinner, so you can paint while you blend!