ge_rik wrote: ↑Mon Sep 02, 2019 7:00 pm
I painted some figures with acrylics and decided to give then a coat of matt varnish. Big mistake! The varnish is still tacky two years afterwards.
Any suggestions?
Change to another brand of clear coat......
I've had no end of trouble with clear finishes off and on over the years.
I used Humbrol Matt Cote and Satin Cote for many years, but when Hornby took over Humbrol they lost the plot. About the time I retired and moved into Garden Scale my last bottle of Satin Cote ran out and the replacement was made in China.
It was used on the first of my passenger car models and while it was touch dry overnight, it never really set hard. If you picked up the models and held them in a tight grip the clear coat would soften slightly with the heat in my fingers and have a very slight tacky feel to it. I noticed late last year that the finish had finally hardened, it only took 5 years, almost to the day.....
I haven't used any clear coat made by Humbrol on a model since then. I bought a bottle of Satin Cote to test after production moved back to the UK, but it was still the same. The polyurethane varnishes that Humbrol sell in tinlets has also changed and I stopped using that when my last tin of 'real' Humbrol ran out.
The enamel colours dry OK, just not the clear finishes. My problem with the colours is that the colours were once extremely stable from tin to tin over decades. When Hornby took over, a lot of the colours changed noticeably. I haven't bought a tin, or bottle of Humbrol clear finish for at least five years years, or their enamel tins for about two years.
I've currently standardised on Revell enamels. The Revell clears soften with heat, but the enamel colours are stable at steam loco temperatures, so I use the enamels on all models and use a locally made brand of hardware store satin varnish as the final clear coat on garden scale models. It sets rock hard in a couple of days and doesn't soften on steam locos.
Revell don't do a satin clear, so I mix their matt and gloss clears 1+1 to get a satin finish. I'm still using the Revell clear finishes for HO models as heat isn't an issue. Revell clears have some strange characteristics when spraying though and I may yet change to the hardware store varnish for all clear finishes.
I don't understand the mechanism, but Humbrol aren't alone in selling clear finishes that can take geological time scales to completely harden. Now that I'm retired and have no chem lab access, I just spray a test panel until I find a brand that gives me the results I want. It isn't a recent problem, I've got a couple of HO models that were painted in the late '70s, which was the last time I used a spray can on a model as it happened. The finish did eventually harden completely, but it took 20+ years.
Remember though that I regard spray cans as an invention of the devil and use an airbrush for all my model painting, so none of these ramblings may be related to your problem with the paint finishes you used.
Waterborne acrylics are lacquers and dry by evaporation of the water and solvents, but varnishes are more akin to enamels and dry by crosslinking the resins on exposure to air. The two types can interfere with each others drying mechanism and the solvents used in some types of paint can attack other paints.
With so many paint finishes available and unknown incompatibilities between them, all you can do is test various combinations until you find one that works for you.
Regards,
Graeme
