Cracking in paint

[Harquil]

Morning all

I’ve been spraying a bureau in the garage as opposed to my workshop (more space in the garage) and I’m getting cracking all over the paint job.

Im using Morrells pigments water based lacquer, I’ve sprayed small bits in my heated workshop using a graco ultra, which has come out brilliantly but I’ve had to move the bigger unit to the garage,which isn’t heated, for space.

Just wondering if the fact that the garage isn’t heated is having an effect on the finish and making it crack.

 

[Sgian Dubh]

It's possible a cold work area may be having an effect. However, I suspect another potential likely cause of your cracking problem might be overly thick application of spray. Without knowing which specific product you're using, if it's their 8FM/Fastmatch Severe-Use Waterborne Colours, for instance, Morrells' guidance is the stuff should be applied at a rate of 75g/m² per coat over primers 8005/501. This information is available at their website.

Typically when I spray pigmented lacquers (e.g., pre-cat lacquer) I aim for a wet film thickness of approximately 80 - 100 µ (microns or micrometers), and apply two coats, ideally one primer and one top coat, but three coats might be needed to hide the primer. If the finish you're applying has, let's say for discussion, 50% solids, then half of the wet coat is solvent which evaporates. So a wet film 100 µ thick will end up ~50 µ when the solvents have left: three applications will therefore result in a dry film thickness of about 150 µ.

You should probably contact Morrells to see what they recommend as a wet film thickness to achieve their recommended 75g/m² per coat (if that's applicable to your product), and to find out at what temperature and relative humidity the stuff works best. This information may already be available (I don't know because I haven't searched) through product use and application sheets that you can download from their website. Slainte.