Enamel Lacquer Acrylic compatability

Very true Phil. I no way does Acrylic mean "water based". But, generally in the modeling world, paints with Acrylic polymers are formulated to be water based. The main thing is if you are using a hotter solvent, like laquer, over something non-laquer, just apply it very carefully misting it on with the airbrush.

hypertex

One myth is that all acrylic paints are water-based. There is no rule or law that says paints labelled acrylic must be water-based. Most acrylic paints are water-based, but that's because many acrylic polymers are water soluble. But acrylic polymers can also be soluble in alcohols, esters, and such. The term "acrylic" refers to the paint's solid film-former (aka binder). In chemistry terms, an acrylic polymer is based on the structure of acrylic acid.  Thus if a paint's solid film-former is an acrylic polymer, then by definition it is an acrylic paint, regardless of which solvent(s) is used.

Tamiya's acrylic paints are not your typical acrylic paints. Tamiya uses alcohols and a glycol ether in addition to water as a solvent. But they as still acrylic paints. While Tamiya's acrylics probably are not lacquers, there is no rule that says a lacquer paint cannot have an acrylic binder (hence the acrylic lacquers in the auto industry).

I have been saying this for years, but it's hard to change preconceptions. People try to say Tamiya acrylics aren't "true" acrylics because of this that or something else. They are indeed acrylic based because they use an acrylic polymer binder. They are, however, remarkably flexible in that they are compatible with a wider range of solvents than many other paints.

I never bought the rule that says you can't apply a lacquer over any other type of paint. There are too many exceptions for this "rule" to be useful. As Doogs mentioned, there are many formulas for paints and the groupings are confusing. Lacquer and enamel paint have never been precise terms--they are not named from their ingredients. There is no universal governing body that sets out precise definitions for these types of paints.   As a result, we get confused.

One myth is that all acrylic paints are water-based. There is no rule or law that says paints labelled acrylic must be water-based. Most acrylic paints are water-based, but that's because many acrylic polymers are water soluble. But acrylic polymers can also be soluble in alcohols, esters, and such. The term "acrylic" refers to the paint's solid film-former (aka binder). In chemistry terms, an acrylic polymer is based on the structure of acrylic acid.  Thus if a paint's solid film-former is an acrylic polymer, then by definition it is an acrylic paint, regardless of which solvent(s) is used.

Tamiya's acrylic paints are not your typical acrylic paints. Tamiya uses alcohols and a glycol ether in addition to water as a solvent. But they as still acrylic paints. While Tamiya's acrylics probably are not lacquers, there is no rule that says a lacquer paint cannot have an acrylic binder (hence the acrylic lacquers in the auto industry).

Paint incompatibility happens when the solvents in one paint dissolve the binder in the paint underneath it. Since paint companies keep the binder ingredients secret, it is not possible to predict which solvents will dissolve which paints. Hence the cardinal advice is to always test on something other than your model, and always allow the paint to fully cure before applying another paint.

Chris

The general rule of thumb is that the "hotter" paints should not be applied over "cooler" paints.

In general terms, in order of "heat",

1: lacquer
2: enamel
3: acrylic

That is to say that enamels and acrylics can be applied over lacquers and acrylics over enamels safely.

However, we know that for many years, modellers have applied lacquers in the form of Testors glosscote/dullcote and Tamiya spray clear gloss/flat over enamels and acrylics with no ill effects.

This is often down to technique. Always allow sufficient time for the colour coats to fully cure before applying the clearcoats. When applying the clearcoats, apply the first few coats as a light "mist coat", allowing each successive coat to dry before recoating.  This forms a barrier over the underlying paint which protects it from the harsher solvents in the lacquer.

Many a modeller has ignored this process and applied a wet coat directly to their colour coats and watched in horror as the colour coat wrinkled and shrivelled before their eyes.

As mentioned, in recent years, the line between the different paint bases has become blurred and indistinct. It is now possible to have lacquer, enamel and acrylic paints on your shelf and use a single (lacquer) thinner  for all three (depending on brand of paint). So to reiterate what DOOGSATX  said above, if in doubt, test on scrap first.

When it comes to paint, there are so many different variables that the definitions of lacquer, acrylic and enamel are almost laughable. I mean, Tamiya's often called an acrylic lacquer. Gunze has something called "solvent-based acrylics". I've had Gunze gloss clear attack other Gunze paints and Tamiya paints, but not MM enamels.

The best (and only) bet if you're unsure it to test the combo out ahead of time. But if it works and has worked for years, keep on keepin' on in my opinion.