I have encountered an issue. Don’t we all?
I spray Mig Ammo primer. Then top coat of Mig Ammo paint. Then using the oil dot method I weather the subject. I use odorless white spirits. Always worked fine. Now on my latest build with just a few brush stroke to remove the oil paint I’m cutting right through the top coat. Removing not only the oil paint but the acrylic top coat/s. Any idea what has happened?
bruce
You said “Always worked fine”. Did you change brands of thinner? Some are hotter than others. Is the type of Mig paint the same? I haven’t tried the white spirit s yet but I read warnings from others that said you only get 1 or 2 strokes otherwise the acrylics start misbehaving.
Thanks. Yup nothing has changed. I have always been aware of over doing it. This top colour took a few days to dry completely. Maybe our humidity is influencing the results. (Now 30 each day and 90+% humidity. Yay summer is coming. Boooo). Top coat just not hard/dry enough?
The upside is that the primer is oxide red so no harm. But I’m still curious.
bruce
Personally I never work oils over my acrylics without a varnish layer between them even though I’m using art aisle thinner predominately. You didn’t mention this step so if you did clear coat prior to oils did you use a different clear coat?
I use oils with a varnish coat as a filter . A satin to do pin washes.
The trick for me is to use naptha with the oils .
It will not harm the acrylic
Thanks guys. I don’t use a clear coat. I’ve never had this issue before. Maybe it is the fact that the paint was applied during high humidity and the top coat has never cured properly.
As a test I found some parts painted but not used in the kit. Same method but with 2 different thinners. Same results. So my guess it’s not the thinners.
bruce
OK I THINK I know what is happening. Between builds I tend to forget things!! 
I think my brush has been too dry. Oil paint dots on. Damp brush to remove the oil. With a too dry a brush I was scrubbing at the oils to much and going through the top layer of paint. (Just like happens with chipping). So damper softer brush. Get in get out. If I’m not happy I come back later. Give it time to dry out a bit and have a second go.
Lesson number 34448
bruce
Try switching to Turpinoid instead of white spirits.
Thanks. I’ve tried both white spirits and turps. I think it was mostly user error!
bruce
Have you tried water mixable oils?
Water mixable oils? No.
need a separating layer of varnish. and give the acrylic paint to polymerize for at least a day