Is there anything wrong with mixing incompatible paints?

Question

I randomly stumbled upon this video https://youtu.be/TuEBKV6T5aU?t=31s

Where a user modded his Nintendo 64 and gave it a "custom paint job."

He mentions that he used 2 types of paint that were NOT compatible with each other in order to form this paint-job. He said the paints themselves try to separate which causes the cracking effect.

Personally, I really like this, and would like to do something similar with a project I'm working on.

My questions are,

1. Is there anything wrong with mixing paints that are NOT compatible? From what he mentions it's just that the paints don't mix and separate from each other, but is there any danger in doing this by mixing things that shouldn't be mixed?

2. Are there specific paints that would cause this effect, or would any 2 incompatible paints do this no matter the paint used? I'm essentially interested in other cool effects that could come about by mixing paints like this, but don't want to encounter any dangers.

note: I'm not sure if this is the right place for this type of question, or if this is more suited for the Chemistry-Stack?

thanks

Answer 1

So, from my experience...

1. Wrong? No. Basically, looking at the major art paint options I can't see any that, when combined, would result in a dangerous mix. Some, however, will mix a bit better together than others.

2. Yes and no. The key to the cracking effect is difference in drying times, some paints dry faster than others and when you apply a fast drying paint over a slower one, the result can be that the upper layer will crack. The "no" part of this comes from the ability of some mediums to adhere better or worse to each other. For example, acrylics use water and oils, well, oil. When you try to apply acrylics over oils, it will crack and split (your desired effect), but it will also tend to flake, which is less desirable. In any event, some mixes will probably work better than others, but there's likely to be some trial and error involved.

So, my suggestion is that if you're going to give a go, do so on some items you don't care about, but that also has the same surface material and try a few combinations using some student-grade paints (much cheaper).

Answer 2

The technical term for the technique he's demonstrating is "craquelure." You might get some mileage out of researching how this technique is typically achieved. Craquelure is commonly done in ceramics, which might not be useful to you, but there are other media that achieve the same thing in ways that might be useful for your application.

One way that I'm familiar with to achieve the "craquelure" effect he demonstrates is to add something to the paint that will shrink as it dries/cures. A common trick in prop-making is to mix water-based glue in with water-based paint. The common basis makes them mix well, but as the glue dries it will shrink and crack. Many glues are specifically formulated to stay the same volume as they dry, so you may need to experiment to find a glue that will actually shrink enough for you.

I wonder if a flour and water paste would work...