The Little World

A recent paint job that required three colours sprayed onto a model aircraft fuselage went pretty well – the lightest colour first and then two more in layers with masking tape application between the coats. I have the business of dilution and air pressure pretty well sussed for the types of paint.

Note that in this instance I am trying to use up the aqueous acrylic paints that have accumulated and then replace them with solvent-based ones. The warm weather means that the aqueous paint does dry pretty fast anyway.

I did test that the layers had cured before the masking tape went on, but found that after it came off from the gloss surface there was a deposition of adhesive gum left from the tape. It was minor, and the effect disappeared under an eventual semi-matt final coat, but it could have been yet another spoiler.

I thought at the time that it was the effect of the hot weather on the masking tape, so I made another series of tests. I put several types of tape on matt and gloss surfaces and left two old sample mules in both the hot workshop and the cool computer office. I wanted to see if that adhesive contamination would occur.

Well, it didn’t. Neither of the mules suffered any sticky deposition. But in the meantime someone in the modelling fraternity suggested another explanation…and it seems quite plausible:

The masking tape gum is being re-activated to go sticky by solvents from the paint that hits the back of it and diffuses through. It was suggested that I test this out on another mule, with both aqueous and solvent paint as top coats. This will be an experiment for tomorrow.

The chap at the modelling club also suggested that I switch to Tamiya masking tape as some forms they sell are a vinyl material rather than paper. Presumably this would make it non-porous and not lead to activation of the gum. Sounds fair, though I must say the Ustar paper tape is cheaper and more readily available locally.

I shall let you know how the business works out.