I have a ‘soft paint’ problem on my car (an MGB) which was re-sprayed 6 months ago at a local sports/performance car restoration specialist. This was a full bare-metal re-spray. Even the lightest touch (with fingers or clothing) will leave permanent scratches on the paint surface. I complained about this, and the other day the proprietor of the restorers visited me to see the car, and brought with him the paint retailer and a technician from the paint manufacturer. The technician carried out a hardness test on the paint and confirmed that the paint job was too soft and unacceptable, and would require all or some of the applied paint to be removed and the job re-done.
The products used were:
The paint technician said that there had been insufficient thinner added to the basecoat – he thought it should have been 20%, and said that this is what they (the manufacturers) recommend. I’m surprised that such a small difference could be responsible for what now appears to be a very soft paint surface. He has advised that both the clearcoat and basecoat should be removed before re-spraying.
Later, using a razor blade, I peeled off a couple of square inches of paint. The clearcoat came away with all the basecoat attached, leaving the primers attached to the car. The primers appeared to be fully cured and wouldn’t mark by fingernail. The basecoat layer didn’t seem to be soft – it scratched off the clearcoat as black dust. The remaining layer of clearcoat is very soft, and will mark easily.
Approximate paint thicknesses are:
Primers – 200 microns
Basecoat – 25 microns
Clearcoat – 90 microns
I’ve looked at the Lechler data sheet for BSB basecoat and it recommends a mixing ratio of 1000 parts BSB to 600-800 parts 00741 thinner.
Could the basecoat be responsible for the paint softness?
(Attached photo shows scratches left by artists' small watercolour brush)
The products used were:
- Lechler R-EC epoxy primer + Lechler 29370 hardener (2:1) + Lechler 00516 thinner as required.
- Lechler TI primer + Lechler HS hardener (5:1) + Lechler 00740 thinner as required.
- Lechler BSB basecoat + Lechler 00741 thinner (10%).
- Lechler Macrofan HS clearcoat + Lechler HS hardener (2:1) + Lechler 00741 thinner (10%).
Later, using a razor blade, I peeled off a couple of square inches of paint. The clearcoat came away with all the basecoat attached, leaving the primers attached to the car. The primers appeared to be fully cured and wouldn’t mark by fingernail. The basecoat layer didn’t seem to be soft – it scratched off the clearcoat as black dust. The remaining layer of clearcoat is very soft, and will mark easily.
Approximate paint thicknesses are:
Primers – 200 microns
Basecoat – 25 microns
Clearcoat – 90 microns
I’ve looked at the Lechler data sheet for BSB basecoat and it recommends a mixing ratio of 1000 parts BSB to 600-800 parts 00741 thinner.
Could the basecoat be responsible for the paint softness?
(Attached photo shows scratches left by artists' small watercolour brush)