109 replies to this topic

[germini30]

Will the primer have settled down by e
Wednesday

[Stu.]

I celly topcoated 4 coats to my engine bay the day after spraying 2 coats of celly highbuild primer with no issues.

[germini30]

Ok. Some say to leave it shrink but surely once its dry it aint going anywhere

[Stu.]

Well, to be fair the topcoats took about 4 days to harden, but I needed to get the bay painted and was not too picky about a perfect finish. If I were doing face bodywork I think Id leave the primer 4 days before topcoating. Regarding shrinkage Im not sure, but I guess if you topcoat over primer thats not fully hardened, it could shrink a bit and multiply slight imperfections in surface finish.

As said earlier, the nail test is usually enough to determine when the primer has hardened enough.

[germini30]

Nail test?

[Stu.]

Sorry! Push your thumbnail onto an inconspicuous area of primer. Somewhere to be covered by trim perhaps. If it leaves a mark its not fully hardened. I did this on my topcoat. Left a mark day 2. No mark on day 4. Warmer temperature speeds hardening (solvent evaporation).

[skoughi]

How long were you leaving between coats out of interest? I was too keen when I put my primer on last week and had quite a few spots where the previous coat hadn't flashed off properly . I've flatted back and it's going to need another few coats so going to take no chances and leave at least an hour between coats, my garage wasn't as warm as what I thought!

[Stu.]

I spray the next coat once touch dry. 10 mins normally but variable depending on temp. It also depends on thinner content. Higher thinner content might take a bit longer to flash off but Im not sure. I do everything 50/50.

[167ade]

Barcoated yesterday afternoon. I then primed using high build cellulose primer and am happy to say that there is no reactions anywhere. Primer went on well, I did one light coat followed by three decent coats. Glad I had a respirator on. Went back out the garage after the last coat of primer was applied and the fumes were strong. Looks good so far, hopefully wet flat it Tuesday evening and paint wednedsay afternoon.

 

make sure its fully hard in my expeirence 1k high build takes longer to harden than 2k remember there aint no hardener in it and you have put 3 heavy coats on also remember to spray a guide coat on before you flatten

[skoughi]

Thanks for that stu, I've actually been leaving it longer than that but have still been getting spots where it's been lifting. However I've found a sealer that works so will be using this on the spots that's given problems, I've also bought a 2mm needle and cap so should get away with less thinner and I'm going to leave it even longer between coats, hopefully all this should eliminate the problem!

[germini30]

I got a dehumidifier so will put that on before top coat as well as the heaters I have. Dont matter if its raining outside as the compressor will be drawing in warm dry air. Mind you I was surprised at the amount of water in my water trap after priming.

[germini30]

Just realised that I don't have any guide coat spray. I do have some simoniz matt black aerosol. Will that be ok to use as a guide or may it react with the cellulose as it is acrylic. Its going to be rubbed off anyway but wanted to make sure.

[skoughi]

That's what I'm using, satin black actually which is maybe tougher than matt! Something else to add to my woes!! I would like to have got hold of some celly colour so I could tint the couple of top coats of primer so it gave a better indication of when you were getting to the bottom coats of primer.

[germini30]

Just wet flatted using wet and dry 600 grit. I can see about two or three tiny patches were I can just see the bar coat showing through but I haven't gone through the bar coat. Will it be fine to topcoat over this? Also when painting shall I do a dust coat first then plenty of wet coats?

[Daz1968]

I would put some more primer on these areas and flat again, as any edge between layers is an ideal place for pickling to begin