Slight issue with clearcoat
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First topic so here goes.
I have recently switched to a different clearcoat and since have had a slight issue.
After applying my second coat which is wet and slick but not thick all looks good.
I walk away and clean my gun which takes maybe 5-10 minutes.
When I return the surface is covered in tiny little marks. They are raised, so not silicone or fisheye problem. Looks like very very small solvent pop. They are not noticable unless you get close up. They dissapear once buffed.
I am applying in 1.5 coats. It makes no difference if I wait 30 seconds between coats or I wait 10-15 minutes.
I am using a ultra high solid clearcoat made by Lechler with a fast activator (2:1) and thinner/reducer for 1-2 panel jobs. Tech sheet says 10% reducer. Makes no difference how much reducer I use, same result.
I am painting around 20 degrees celcius. Using a Devilbiss Gti Pro 1.3 (Tekna in US?) Applying the clearcoat between 25-30 psi. Makes no difference what pressure I use.
The only thing I can think of is using fast activator and reducer but at 20 degrees celcius I would not have thought this would be the problem?
Also it happens over the entire panel, not just over the basecoat area.
I am applying basecoat in light/medium coats and letting each cost flash for around 5 minutes until dry.
Any ideas guys?
Try slowing it down and see if the problem persists.
[quote=”ryan999″ post=26444]Try slowing it down and see if the problem persists.[/quote]
I agree.
Some products just don’t like to go too fast.
I have seen it many times; it is called “bumping”. Typically it is caused from too slow of clear in an air dry environment. First make sure the spray booth/car/you are as clean as possible. Next, revert to a thinner two coat application with a long flash between coats also use faster combinations of hardener and/or reducer. An accelerator may be required at 20C (68F). Lastly, make sure you let the booth run as long as possible after you finish spraying. The combination of these things should help. If you do try a slower system, it may get worse but there is only one way to find out.
Good luck!:pcorn:
How old is the clear hardener?
Firstly, thankyou for all the suggestions and help it is appreciated.
I think I will try a medium or slow thinner/reducer because that is the easiest variable for me to change.
Too slow clear in an air dry environment would also make sence as I can leave the first coat 15-20 minutes and it will still be pretty wet.
The clearcoat hardener/activator comes with the clear as a kit so it is made to be used with it, it does have air drying times @ 20 degrees celcius on the data sheet too.
It happens from the day I open it but thinking about it, it does seem to get a little worse as it nears the end of the tin, maybe 3-4 weeks later.
I try to mix it up regular as it seems to settle towards the bottom, I assume this is just a characteristic of HS or UHS in this case.
My supplier sells alot of it, so I dont think it is sat on the shelf too long either.
I shall try a medium or slow reducer and report back.
Thanks guys.
I could, and most probably will be wrong but it sounds like water or moisture in your air line. Why your only noticing it with a uhs clear i dont know but try a disposable air line water trap or opening your air line up and hanging it some where warm and dry over night before you paint.
I had what I thought was solvent pop in a 3-1 clear but it turned out to be water, compressor sweeting. Haven’t noticed it with 2-1 ms clear but spray a 3-1 hs clear and its very noticable, only up close mind but i can still see it under electric light. like I say I could be and probably am wrong.
Speed it up!
Couple of ideas,sounds like the clear is already mixed for the maximum speed,not sure how you could get it faster short of accelerator.Try 2 medium coats with minimum flash,some speed clears work better this way.What could be happening is its skinning over and the extra flash time is not helping.I agree with the others about slowing it down or possible bad batch of hardener.The slower you mix clear will allow you to put on a smoother thinner coat that will flash faster.Let us know what happens….
I wouldnt like to say it cant be a bad batch of activator but I have sprayed around 12-16 litres of this clear, with 3 or 4 batches of activator all with the same result.
Water in the airline could be a possibility as the compressor being used is old and tired and does pump out water but there are 2 traps emptied regularly. I also spray Glasurit gloss with their fast activator and fast reducer with no problems. I dont think the hoses are helping as they are also old and worn.
I wouldnt have thought water would show until it is put in very cold or hot conditions causing the water to freeze or boil and creating micro blisters?
I dont really want to add an accelerator as I am already using fast activators and reducers.
Ill try a medium reducer and see if it changes anything. And empty water traps and try a new air hose.
Thanks guys.
Hello again.
Well I seem to have cured the problem for now.
I tried the easiest things first which were emptying the water traps, which were pretty dry anyway.
And also I started applying more of a medium wet first coat followed by a medium/full wet coat with shorter flash time and it worked a treat.
Thanks for all the suggestions, I would have tried them all if this had not worked.
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