Gel coat question

I have a gel coat question.
On the odd boards I make , I finish with a tinted gel coat instead of paint . On the rails when I thick coat and let drip off the edge , ( oldschool surfboard method ) , I end up with a few , what I believe to be fisheyes ? Between 3 mm to 10 mm in diameter . It's fixable but annoying . How do I stop this ? It happens with different resins and prep finishes . Even have an additive that supposedly stops this . But doesn't . What am I doing wrong ?
When I lightly finish the bottom with a roller it doesn't happen and when I do the thicker deck sugar grip coat it also doesn't happen . I've even done the rails with a roller and slapped it on thick and it bloody happens again . What is it with the rails ?
The reason I do this instead of two part proper paint is because I don't have a safe spray booth and I love the finish the gel coat gives , so sexy . Normal rattle paint just scratches off and is ugly .

Only ever had that issue when the under layer was not prepped properly, either not dewaxed, or contaminated after de waxing, (fat greasy fingers touching it or masking tape glue residue). Could you have contamination?

Thanks guys . Yes epoxy . It probably is contamination . About to do one in a couple days .
Acetone for dewaxing ??

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pepe47 said..

Imax1 said..
Thanks guys . Yes epoxy . It probably is contamination . About to do one in a couple days .
Acetone for dewaxing ??

Don't know if it's necessary to use acetone, I'd use detergent and a scouring pad or 1200 grit wet n dry. I'd also use 2 pairs of food prep gloves to make sure not to contaminate it. First pair you can rip off if you need to answer the phone. Failing that, there is the option of wax remover for panel prep. I'd still wipe it over as it can sometimes leave a thin film. Also, make sure the cloth that you use to clean it up is not contaminated. Grab some microfibre cloths and throw them in a cold wash before you use them.

Do not use detergent and do not use 1200 wet and dry.
Just sand it with 120 grit and keep it clean.
if you feel you absolutely have to clean it with something use acetone as it evaporates quickly and leaves no residue.

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Mr Hooper said..

pepe47 said..

Imax1 said..
Thanks guys . Yes epoxy . It probably is contamination . About to do one in a couple days .
Acetone for dewaxing ??

Don't know if it's necessary to use acetone, I'd use detergent and a scouring pad or 1200 grit wet n dry. I'd also use 2 pairs of food prep gloves to make sure not to contaminate it. First pair you can rip off if you need to answer the phone. Failing that, there is the option of wax remover for panel prep. I'd still wipe it over as it can sometimes leave a thin film. Also, make sure the cloth that you use to clean it up is not contaminated. Grab some microfibre cloths and throw them in a cold wash before you use them.

Do not use detergent and do not use 1200 wet and dry.
Just sand it with 120 grit and keep it clean.
if you feel you absolutely have to clean it with something use acetone as it evaporates quickly and leaves no residue.

Agree, didn't mean to write 1200. Meant to say 120. Yes, 1200 will actually put a shine on the surface.

I don't clean with anything.
Every single product I have used makes it worse.

Don't handle it for a start.
Like Hoops says - light scuff and just coat it.

A 2K product I used to use for firearms had a degrease procedure of
- acetone soak for 20min
- air dry
- bake for 20min at 150-180C to get stuff in the pores to off-gas
- sandblast
- Repeat the degrease and bake at least once, preferably twice.


So if you can't get smooth metal clean without doing the above process, do u really think a wipe over will do it?
The problems with wiping over is you wash stuff down into the weave of the cloth (assuming this is hotcoating after lamination) and you also introduce fibres from the cloth you're using (almost certainly as the fibreglass is rough)

So
-don't touch it.
-hotcoat at the right time before the epoxy is fully cured and you will get a chemical bond OR
- if its cured light scuff with 120 like Hoops says. I think he would know.


In answer to original question its very telling that it only happens on the rails so I say its the touching for sure.

As an aside.... when you bake an acetone soaked item in a home made electric oven at 150C for a while..... you become acutely aware of things like static electricity

^^ Vacuum cleaner with brush fitting then blow it off with air hose. Or just air hose if you don't mind a massive dust cloud in your shed.

Another thing to note here is that what we're talking about is not gel coat, it's epoxy filler coat.
Gel coat is an unwaxed polyester resin that's used in moulds. You're more likely to see gel coat on a moulded boat.

That's mostly correct. Some specific surf board resins like Kinetics you can use a polyester filler coat as long as it's been sanded and prepared properly. It is better to do an epoxy filler coat though.

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IFocus said..

Imax1 said..
I'm now sure it's grubby fingers ,
After glassing , I q cell bog over entire board . After 120 grit sanding it is perfectly dry and smooth . Ask anyone in SE Qld that owns a pool , it is sanded well
However .... there are fisheyes at the front and rear of the board , not just the middle where I would grab and flip it .
I will be super anal clean in a couple days ...............let you know what happens .

The fish eyes, are they in the area you lay the board on the stand?

No.

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Mr Hooper said..
That's mostly correct. Some specific surf board resins like Kinetics you can use a polyester filler coat as long as it's been sanded and prepared properly. It is better to do an epoxy filler coat though.

Why/ that? I'm at the finishing stage of a board and purchased polyester filler for the first time. I'm really fed-up with the long curing time of epoxy coats and the pain of sanding it back.
I know it's less strong and could melt the core, but I'm planning to do a thin layer of epoxy and then rough sand it to give the polyester something to bond to.

Hi NicoDC,
what stage are you up to with your board and what resin have you used up to this point ?

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Mr Hooper said..
Hi NicoDC,
what stage are you up to with your board and what resin have you used up to this point ?

The current one has a few spots where the epoxy didn't cure properly during lamination, so I removed the fibres in those areas, smoothened everything using spackle and am about to laminate the extra patches. It's a prone foil board put together by leftovers, so I don't want to waste to much energy finishing the board.

i've used 3 versions of resion (winter, fast curing and normal curing), poly-pox and now a high level epoxy from HP textiles (German company).
The resion is rather poor and didn't cure properly the last 2 times (a top coat that didn't cure, true nightmare to sand epoxy with the consistency of bubblegum and now the deck laminate that isn't cured in all spots). I mix small batches, use fresh cups and sticks, right temperature,. so no clue how that could happen twice with the same epoxy. I threw out my old scale (it sometimes misses by 2 grams) just to be sure.
the poly-pox was good and nice to work with, but turned yellow-ish
high hopes for hp

regarding the finishing, i guess it is mostly a technique thing + getting annoyed by the hours of waiting while the epoxy cures and the hours of sanding, so I tend to go for the maidentrip before the board is perfectly finished.
i'm yet to find the perfect balance between epoxy and micro balloons: too much and it doesn't spread nicely, not enough and you spend all your evenings sanding epoxy.
polyester filler should solve those issues, that's if the core doesn't melt.
last weekend, while I was restoring the eps/shape with spackle, some spackle got spilled on the fibres and it felt so good to sand it back down in 5 minutes that it got me wondering how spackle would serves as a filler prior to an epoxy finishing coat. It might wash right off after one session, i don't know. There's however probably a reason why no one else does that.

always a bit jealous when I see a video of a shaper on youtube spilling one coat of epoxy coat and achieving a perfect result.

^^^ wall filler - Spakfilla

Yanks love it for 'sealing' EPS blanks before glassing (surfboards). I think that's ridiculous but the seppo's love the stuff. Nico read too much Swaylocks? Nico, spackle over bad glass and re-glass...? Oh my.

You need to figure out why your resins are not going off before you go any further. I'm guess too cold there? Are you confusing 2:1 by weight with 2:1 by volume (that would do it)
Scraping the bottom and sides of the mixing container well to ensure good mixing?

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Mark _australia said..
^^^ wall filler - Spakfilla

Yanks love it for 'sealing' EPS blanks before glassing (surfboards). I think that's ridiculous but the seppo's love the stuff. Nico read too much Swaylocks? Nico, spackle over bad glass and re-glass...? Oh my.

You need to figure out why your resins are not going off before you go any further. I'm guess too cold there? Are you confusing 2:1 by weight with 2:1 by volume (that would do it)
Scraping the bottom and sides of the mixing container well to ensure good mixing?

Select to expand quote

Mark _australia said..
^^^ wall filler - Spakfilla

Yanks love it for 'sealing' EPS blanks before glassing (surfboards). I think that's ridiculous but the seppo's love the stuff. Nico read too much Swaylocks? Nico, spackle over bad glass and re-glass...? Oh my.

You need to figure out why your resins are not going off before you go any further. I'm guess too cold there? Are you confusing 2:1 by weight with 2:1 by volume (that would do it)
Scraping the bottom and sides of the mixing container well to ensure good mixing?

It's what I've been told to use if something goes wrong during shaping (for example a "wrinkle" caused by hotwiring that you can't sand away). No issues so far. I haven't tried to completely seal the blank.

i removed all bad glass. Funny, but the problem occurred on the rails too. Every bit that wasn't completely 100% stuck and cured, is surgically removed. Some of the underlying eps was too attached to the fibres so it left a slightly damaged core. The core was restored with spackle so it can be overglassed and the fibres stick 100% to a bonding area. The next step is to laminate fibre strips on the rails. Then it's time for finishing. I wouldn't fix a trash laminate by laminating over it.

It's a board made from leftovers (biax deck, twill hull), so no need to stop now. The worst that could happen is that I waste some time and learn a thing or two because of it.

Both of my bad epoxy experience happend during winter with temperatures slightly above the minimum required for curing. I make small batches, by weight as indicated, scrape the entire cup (including sides) a couple of mins, let it rest so there are no airbubbles,. only two things I can think off are a broken scale and bad conditions. I have the impression there's a bit more hardener out of the bottle than with perfect mixing ratios.
Epoxy, wonderful product but also the cause of many headaches.