Using chalk pastels and over spraying

Mike, is it armour, aircraft or something else your building.

Thanks guys, I was afraid of that.  I'll try the multi-layer dull coat apps and see how that goes.  Either that, or try to get better at weathering with spray or dry-brush.

Mike

I've used this method to weather model rail cars, and had to do it in layers.

As mentioned earlier start with a clear coat (I use dull), then apply the chalk. Seal with dull coat and repeat as required building up the effect.

I have had the same problem, and have never found a solution.  Some have told me that they use a fixer, and apparently some brands of weathering powder make their own special fixer.  I have experimented with mineral spirits as a fixer, and it might have helped.  The mineral spirits allow the powder, or chalk, to flow into recesses, and when it evaporates you get a "dusty" line.

But I have to say that nothing I have tried really works well.  The commercial weathering powders I bought hold up slightly better than when I used chalk, but would still disappear.  I  now do as Bish suggested, and leave the weathering powders without trying to clear coat them.

I had exactly what you described happen to me, had a kit that I thought looked good, put a dull coat over it, and there was not a trace of pigment left!

I concur with Bish.  Any clear coating you put over pastels will greatly reduce the effects of them.

Everything i have read says they must be added after the flat coat, there's no other way. They are quite resilient as long as its not handled to much.