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post cat lacquer/cv wet coat thickness1/5
hello every one
I have begun spraying a post cat lacquer wich is supposed to have a "near conversion varnish" performance. Basically is is supposed to be a CV with added nitrocellulose.
I was a bit disapointed in its resistance. although I it resistant to water and household chemical I can scratch it to bare wood diging with my nail.
To diagnose the problem I applied the post cat as self sealing to barewood. It seems that the harder to wood is(purpleheart) the more resistant the lacquer is and vice versa. If I scratch enough to denth the wood the lacquer is comming off.
I also thin my lacquer using the proper reducer in the pds and there is no limit to how much thinner I can add. The manufacturer state that applying many low solid coats vs one high solid SHOULD not affect its properties.
The only variable I havent tested is wet coat thickness( and dft calculation). I usually apply only I vinyl coat thinned 50% and one post cat coat thinned 50%. in order to not go over the dft limit. I have also tried applying as much as 4-5 coats undiluted and could scratch the same way.
This has left me thinking that I may applied my coats to wet or maybe too dry. I generally do only one pass and it stays full gloss for 3-4 min before drying. I will get a wet film thickness gauge tomorow but couls this be a culprit? I have read many times that dryspray can cause adhesion problem? also many people makes many passes for a coat.
I would had that I am used to use floor poly applied on trims using foam brush so maybe my expections may be too high. Although I have no experience with CV and similar some people said that they are supposed to be tougher. is it unrealistic.
Could this also be a symptom of exceded dft althought I have a piece than was sprayed with postcat unreduced and with more coats over a year ago without crazing.
How long are you waiting before you do the scratch test? What do the specs say about a full cure time?
When you scratch it does it shatter and turn into a powder or is it kind of gummy and soft?
It should be hard, and it should fracture before you can break through it. If it's gummy than it's either not fully cured or it's catalyzed incorrectly.
Brush on Poly generally takes 30 days to cure. I don't think there are many tougher finishes than (cured) brush on Poly, it is very resilient.
It is not soft when I scratch it. if I scratch it lightly and repetedly I get a powder just like when scratching a lottery ticket. adhesion is not an issue since I applied various kind of tapes on my pieces overnight and none of them pulled the finish.
I suppose this is the kind a durability you can expect from a cabinet finish. Something that can resist cleaning water and soft clothes but not repetitive nail dragging accross the surface
Doesn't happen with ML Campbell's Krystal (its a CV). Sounds like you need to try something else.
It's my experience that when a product is marketed as being as good as something else, IT'S NOT ! It's just marketing hype.
If you are using vinyl sealer under a post-cat finish, you need to catalyze the vinyl sealer as well..... at least with every other vinyl sealer I've ever sprayed.
It may not use the same catalyst or catalyst ratio. But my vendors have always required a catalyst in the vinyl.
Be sure you are curing this stuff at 70 degrees Fahrenheit or higher.
My suspicion is that you have an inferior product. I've sprayed (on a commercial level) 5 different major CV lines and NONE of them would scratch off as easily as you say once they've hit a good 8 hour cure.
Find yourself a true non-yellowing conversion varnish and skip the sanding sealer/vinyl sealers. Just spray it self-sealing, 3 coats, and you'll be quite pleased, as long as you're using decent spray equipment.
thanks everyone for your responses
I got my hands on a wet film gauge and mesured my coats. Is it me or cleart coats are very hard to mesure. Dipping into the coat has given me poor results. I ended up dragging trough the wet film and notice were the gauge dragged it.
To my suprise my wet coats were maybe just 1tho and the manufacturer recommend 3-4tho wet thickness.
Could my problem could be caused by wet coats not thick enough (ie dry spray).
Anyways back to the test pieces I am now making 3 passes with the same fluid pressure and the gauge scratch between 3-5 tho.
Will report back
Dip the gauge into the wet film and then pull it out. Press the edge of the mil gauge against a pc of paper for a few seconds and remove. It'll leave wet marks that should show you where the gauge was wetted.