Man, i thought a nice buffed, waxed, and ready surface would be great. NOT for some reason when i brushed on my gelcoat for the first time on this mold, the gel coat tried with some spots with missing gel coat =( … i brushed on a 2nd layer the next day after drying… and it bubbled b/c of to much mekp =…
what can i do to avoid this.
the problem is that you are brushing the gelcoat on, if you spray it you will not have this problem
Hey man, can you elaborate on why it happens? I assume he means he is getting a little transfer from the mold to the part?
I’ve had PER gel coat get lots of tiny gas bubbles in it. I don’t think I over catylized it, but it was just really hot outside when i was working with it.
is this a common issue… if too much MEKP is used then tiny gas bubbles form?
the problem is there is no surface tension on the mold, so when you brush on the gelcoat you are apply larger amounts of gelcoat then you should which then causes the gelcoat to pool and fish eyes. gelcoat should be thin, thicker gelcoat can cause it to gas off and create little pinholes/ bubbles.
you also may have added the second layer too soon, first layer is still gasing off when you apply the second
Would you want to hazard a guess about the brushable gelcoat I’m using… Do you reckon that they formulate it to avoid things like that, when they’re making brushable stuff? Or maybe it’s just a little thicker?
I believe its just has more filler in it to thicken it?
There are brushable, and sprayable gelcoats. And you are correct to say that they are formulated differently.
If you plan on brushing its essential that you buy brushable gelcoat. Otherwise you will be using a very thin gelcoat, which will leave brush marks and low spots all over.
If you apply a second coat of gel ontop of relatively green gel make sure the second layer is mixed with a slightly higher percentage of MEKP. The other sure fire way to get spidering is waiting way to long before applying the second coat as the MEKP will attack the previous layer.
Arrrgh! So much to go wrong!
i was to lazy to spray… i usally spray it all… ill go back to it. just such a small part i dont want to wip out a quart size cup… i guess ill use the small hvlp i have and have been using. thanks hojo…
Malcom… don’t use gel coat for carbon fiber parts. If your making fiberglass only parts then yes use gel coat in the mold, but spray it in there. For molds, tooling gel coat is brushable…it’s thick.
Yep, just for my molds… I did wonder, my stuff doesn’t say ‘tooling gel coat’ on it, but I suspected that that was the intention of it, being brushable and all?
Wonder if there is any real need for spray applied “tooling” gel coat on small moulds, that are not going to be used for reasonably intensive production work?
Are you waxing the mold only, or are you waxing and PVAing? The reason I ask is that I have found gel coats can fish-eye on highly polished and waxed molds,(as hojo said) but won’t on PVA.
nothing of my has ever fish-eyed. even when applying more then 1 coat of gel-c. but, i am using a new product zyvax. great GREAT! stuff… but wow way to shiney =)… ive never tried pva in the mold then gel coat etc… i might try it tonight and still try brushing… BUT i think the pva will also do the same affect as the gel-cat. it will just move around and leave dry spots