I've been using PC for 3 years now, but have been curious about HT. I suspect that at a certain volume, it might be a quicker overall process than PC. We shall see!
I did a sample of my "C" grade keepers.
Read the stickies and searched threads but here is a concern. The bullets are absolutely passing the smash test, but are failing the transfer test (rubbing on an acetone-soaked rag for 30 seconds). In each test, a little color shows up on the rag. I have not been able to resolve the transfer test.
Colour removal after adequate bake is mainly caused by wiping off little blisters caused by inadequate drying. What happens, is trapped moisture, when heated expands at 100C about 1000 times its own volume. This causes tiny blisters which are brittle after baking. The blister "bubbles" simply rub off even if you don't use solvent, by the abrasion of rubbing. In majority these shoot OK< but don't look so great with being shiny and smooth.
I revisited the directions carefully.
More acetone is better than less. Check. Tried adding a bit more to the mix than the recipe called for.
Thin amount of coating. Check. Barely any on there.
Oven temp. Check. Pre-heated and verified by an oven thermometer. 9 minutes bake time.
Depending on oven type, and adequate air circulation, may be 9 minutes may not be enough. You really need to concentrate on temperature of the load instead of oven temperatures. The load must get to 180C and stay there or above for about 2-3 more minutes to adequately cured. Oven temperature really does not tell user where his load is at any time with temperatures.
Instructions said that too low a temp could be a culprit. So I tried one batch a little over 400 in case my thermometer was a little off. Turned almost brown. That tells me that it had enough heat. Same result with the transfer test.
This is telling me, that you had adequate if not too much heat for time spent inside oven. Please refer back to what I said about load temperatures.
Letting them completely dry before baking. Check. Definitely dry. Not at all tacky.
This area is a difficult one. Products may "feel" dry, but in fact moisture is trapped below a dry skin of coating. When heated, the moisture will form bubbles which are set in the coating film, after baking
Here is one lot of 401638s with 3 coats of
HT powdered Brick Red.
Not sure where to go next. One thing that occurred to me is that the powder has been sitting on a high shelf in my garage for 3 years where temps have been hugely variable (sub freezing to over 100f). Does it deteriorate? It is likely user error, however, but curious about storage concerns.
Unless product is in direct sunlight, it should be OK, but may have absorbed moisture with storage. This moisture must be dried out afte coating.