I paint gaming miniatures (the type used for Dungeons and Dragons, etc) for my pocket money. I'm working on a commission, and the brown paints I'm using on these two minis are crackling badly. I'm having to cover up and cover up and cover up, eventually losing the details.

Here are the facts of the case:
1) the miniatures are plastic (the Bones line by Reaper Miniatures)

2) I used a white spray primer I snagged at the hardware store (That seems to like to stay sticky forever. Don't know if it's a salient point, but I figured it might help). If you'd like to know the brand name and exact type, I can dig the can out of my supplies.

3) The paint I'm using is acrylic.

4) only the browns are crackling, none of the other colors. The browns I've used are: Oiled Leather, Ruddy Leather, and Troll Shadow, all from Reaper's Master Series line.

I've never had a paint crackle like this before! Help!

I found this, from a site that sells the paints. It includes 'instructions'.

https://www.coolminiornot.com/shop/reaper-master-series-paints-ruddy-leather.html

Have you tried contacting the manufacturer, directly?

It is crackling because you are placing a fast drying paint (acrylic) onto a slow drying surface (primer). This to me indicates you are using an oil based primer and a water based acrylic. Some acrylic enamels will dry over oil based primer and some, as you've found, do not. Since you cannot rough the plastic surface of the figures before applying a primer, you should use a water based primer and then an acrylic enamel paint. The enamel will have less of a tendency to crinkle because it is a hard drying paint.
See:
http://en.wikipedia.org/wiki/Acrylic_paint#Differences_between_acrylic_and_oil_paint
and read the "Differences between acrylic and oil paint" article.

Another possibility is that you have come across a paint manufacturer who uses the same labeling for water based colors as it does for oil based products, allowing for someone to pick up some oil based brown with the other waterbased colors. The labels must be read. Sometimes the oils of a primer will coat a surface and prevent an acrylic from adhering thus allow floating plates of dried material (crinkles).

Then I found this paragraph under "Primer (paint)" in wiki, and note the part about "for plastics... are not water based..." and make a decision to switch to an oil based enamel for your final coating.
Primers for plastic
Using a primer on surfaces made of plastic is only necessary when making a drastic change of color (going from dark brown to white, for example), because most household plastics are not very porous and are not easily damaged by moisture; or when a long-lasting coat of paint is desired. A primer will reduce the number of layers of paint necessary to completely cover the previous color, and will help the paint make a thorough bond with the surface being painted. Because most paints and primers designed to be used for painting plastics are not water based, an important point for choosing a primer for plastic is making sure the primer's propellant or solvent will not dissolve or warp the plastic part itself (e.g. most common household spray paint will damage polystyrene foam). Both the primer and paint should be tested on a small hidden spot of the part being painted.


So, from what I've read, you really shouldn't need a primer on plastic (just be sure it is chemically clean and dry before painting). Primers are either oil based and shouldn't be mixed with acrylics or they are LATEX (a rubbery material) and are not a good base for a hard acrylic coating. Or, you should just go with an enamel (like Testors) on the plastic pieces. Testors paints have been used by makers of plastic model cars, boats and planes since plastic models have been around. I do not work for Testors but have used their product for fifty years successfully.

Thanks, this is all helpful stuff to know.

As for just not using a primer, the Bones minis are intended to not need a primer, but I've found that about half of the minis, the paint wont stick. So I prime them all, just to be sure. Also, since these are meant to be handled a lot at a gaming table, I want to make sure the paint adheres. I guess next time i'll just need to read the primer can a bit better.

I've used Testor's enamels before, and don't really like them. They don't get matte enough to believably look like cloth or flesh. But they're wonderful for armor pieces, lacquer pieces or colored glass bottles and the like that the character might be wearing or carrying.

I've been painting minis for around 7 years now, and this is the first time I've had anything like this happen. Then again, its also the first time I've used a primer from a hardware store instead of a hobby shop, and the first time I've ever really used the Bones minis on a large scale (it's a brand new line). I guess its just a case of trial and error, eh? *sighs* Well, I'll know better next time.

Thanks again guys. Hopefully I'll be able to salvage these frost giants without having to PineSol the paint off.

Another pre-paint surface preparation without using a primer is to wash the object with Tri-Sodium Phosphate (TSP). It acts like a chemical sand paper on glossy surfaces, like what you seem to have encountered with these models. On a large production run the manufacturer may have been using a mold release agent to make it easier to separate the formed models from the mold. That type of residue might hinder your paint application and it was just coincidental that it was where you applied the brown paint?

Well, I always make sure to wash the minis before painting (usually with a dead toothbrush and dishsoap) so as to get the mold release stuff off - partially because of paint slippage, and partially because it clots up the details. Its a habit I picked up from when I worked on metal minis. If the paint problems had cropped up on only one mini or on an area of one that effected the other colors too, i'd have written it up to that and moved on. But one specific set of colors on two minis? That's weird.

I'll have to look in to the TSP thingy though. I'm working on a shoestring budget, but if its not too spendy, i'll give it a try. Thanks for the idea.

I'm pretty sure I've figured out exactly what's up. My metal minis have never had this problem, and only the plastic ones do, and only with this new primer. I think it may be a bad reaction between this new primer and the plastic of the minis. Guess I get to find the budget for a different primer.

A bit late, but just to say I had the exact same problem with the Reaper Minis Bones figures. The acrylic would 'bead' on the figures and would peel off or crack in places afterwards. The things were a nightmare to do. I'm a professional figure painter, and I've never had problems like that with other plastic figures.