Hey guys, I have a couple pieces that for some reason have pinholes. I just pulled them from the mold and hate to throw them away. I was planning on clear coating this weekend. Will the clear coat cover up any small pinholes or is there another way to fix this before clear coating?
Try and fill them with super glue if you have steady hands. You could also try filling them with syringe and some clear coat.
If you spray over them usually they look like bubbles.
The clear will sink into the pin-holes, it will eventually cover them, but you’re in for a weekend of wet sanding. It isn’t uncommon for the pin-holes to happen in an infused piece, usually, it is a sign of an infusion that may have been a little on the quicker side.
One tip, depending on the shape of the composite, you can flood coat it with a pubble coat system to seal the pin-holes in, once dried you can dry sand it with 400 grit and basically flatten it, I usually try to remove most of the puddle coat since it has no UV stabilizer. Once done, I prep the piece with a degreasing wash, let it dry, use a tack cloth to remove any fine particles and clear coat.
Usually I can get away with one maybe 2 coats of clear, quick wet sand with 1500 and polish. I used to use clear to accomplish any pin-hole issues but just couldn’t handle the multiple clear/sand/clear/sand process so I moved to the puddle coat scenario.
The bad part is this only works on relatively flat objects. The other thing you can do is to brush the clear on the piece and sand it smooth, again with 400 dry. At least in the effected areas where pin-holes are at there worst.
Hope that helps…
Thanks guys!!
I’ll see what I can do this weekend 
You can use black filler to close the pinholes, there are also clear filler availeble. If you want to close the pinholes by clear coating you have to close fill/swimm them with a needle.
Only clear coating does not work (in most times). If it is a small part I would infuse it new, less work than closing pinholes.
What do you use for a black filler?
Pinholes are a pain to get rid off, I usually flood them with clear coat or fill them with a needle or brush whatever works better and then sand flat and reclear.
Puddle coat?? how this works?
Indeed there is a clear filler available???
Map Yachting has “bouche pores” which is a pinhole filler. Wipe on, let dry, touch with scotchbrite, and clear coat.
I guess you could make your own with a 1K PU and carbon black powder. (although it is messy)
This is why clear-coating the mold is so nice.
Anyway, I used to mix up a small batch of 2K clear and wipe in onto the surface with a cloth in circular motion. Then I would force cure it, sand smooth, and spray the final. This did the trick most of the time…but not all the time.
It’s like a mirror coat, think of it as a bar top epoxy flood coater…because it is so thick, you can pour it in the area with bad pin holes, it self levels…then sand it off or you can use the needle method to fill the holes individually. It’s thicker than regualr clear and super high gloss. Usually I pour a bit on, spread it around with my finger (in a glove), don’t break the surface tension of it on the area you are spreading it. I let it sit for 5 minutes, make sure it has filled the holes and the coating is level, then I spray it with acetone to break the surface tension (it removes bubbles) - exact same effect as a torch, you just have to let the bubbles rise to the surface before you hit it with a spray (mist) of acetone. Works like a champ and reduces clear applications, once sanded you would never know it was there or done.
PS…a mist of acetone guys, doucing it with acetone will make it run and it won’t dry…
^^Agreed, but in large moulds clear coating it after it has a layer of wax in it is not fun…fish eyes like a mofo…I think the application is relative flat or organic shapes works wonders, we do it too…but in a mould that has multiple angles, drafts and vertical up-sweeps and such, it will run and it will fish eye…
When the part is pulled (complex shape) the clear cracks and now it needs to be sanded off before it can be cleared…it works, but not for everything.
Just my 2 cents…
A few thoughts:
I you like wax for a release you might consider Dolphin Wax. It will eliminate your fish-eye problems. It was developed for paint in the mold operations.
I always shoot a fine mist coat of clear mold, let it set, then progress with coverage coats. This technique works on top of high slip semi-permanents. If you use a high velocity clear then you can speed up the waiting time. If you shoot a coverage coat right off the bat then it will fisheye like mad.
What clear are you using that will crack? Many 2K clear manufacturers make a flexiblizer that will increase the elasticity of the paint/clear.
It’s rare that I tout a product as being wonderful, especially when it has wonder in it’s name, but get this Loehle wonder-fil. The pint size can will last you forever. Basically you wipe in on. I usually just put a dab on my finger and rub it into the pinholes. Then you wait a 10 minutes or so and wipe it off. Then paint.
I don’t like the paint over them option. The paint doesn’t always soak in to the hole. It just bridges it. Then the hole reappears when you sand the clear. Or it reappears months later for no reason at all.
I have tested the Basco System Filler and clear coats. For myself I make the part new, I never repair or clear coat.
I think it is difference in the types of products we produce, 80% of my moulds are larger than 5’x5’ - when demoulding the part will flex, we use or have used for in mould coating PPG clear, Epifanes clear varnish, Duratec & a host of others. Some work well, just about all clears (quality) ones at least have (flex agents) etc…Don’t get me wrong, I didn’t mean every time it has cracked, just that it has happened.
^^Is it clear in colour?
Did you have good results?? I couldn’t make it work,after clear coating I still could see pinholes.
We made two test parts and they were perfect. If you go very very close you can see the pinholes if you know where they have been, but the result was fine.
I applied it like a filler, let it dry and then light sand it with a scotch brite and clear coated, even after clear you could see the print of the pinhole, and the second thing i didn’t like was that a black dot could be seen between the intersections.
I worked with the clear filler for visible parts.
I used shoe polish once. I had to spray paint a carbon boat white. I warned him that pinholes might show up. Finally there was a 5x5cm area which had pinholes. The customer went beserk, and demanded a respray. I filled the holes with shoe polish, the customer never noticed.