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Hot coat hints and tips

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alpaia
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Re: Hot coat hints and tips

Postby alpaia » Sun Jun 07, 2020 11:25 pm

Thanks TomW for the detailed process, I will apply it next time.
It looks like I was ok with avoiding contamination & cleaning with alcohol (no fish eyes) but neglecting the dropping temp and de-gassing of resin so always getting bubbles.

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Re: Hot coat hints and tips

Postby RichR2 » Sun Jun 21, 2020 7:03 pm

TomW wrote:
Thu Jun 04, 2020 9:25 pm
jaros wrote:
Wed Jun 03, 2020 7:06 am
TomW wrote:
Tue Jun 02, 2020 9:43 pm
It's more involved than that.

My entire process:
Clean shop, vacuum up everything. Preferably a day before.
I vacuum off the board last on that clean up day.
Don't turn on your vacuum cleaner the day you do the coat. Keep air still.
I put on vinyl gloves.
Wipe off board with tack rag, wipe off board with denatured alcohol ( dna). Use good lint-free paper toweling.
Tape rail. Wipe off with DNA, tack rag again.
Turn off heat in shop.
Mix and degas resin.
Pour on resin, using high quality brush, brush diagonally one way, then the other. Brush rails, brush longitudinally from center, finish with rails.
Get out of shop.
3 hrs later, remove tape from rail and turn on heat to 18c.

The principals are: dust free shop, no air movement, dropping temperature, no hand oils on board, tack rag removes dust stuck to board from static charge, no air bubbles in resin, don't over work brushing that can add bubbles.
Nice description!
Do you clean the brush for another use or do you use a new brush every time? Thanks!
New brush every time.
/quote]

Just followed all your suggestions Tom, brilliant finish obtained, which wont require much sanding. Thanks for the advice.

Matthijs94
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Re: Hot coat hints and tips

Postby Matthijs94 » Wed Dec 23, 2020 9:12 pm

How much resin do you guys usually use for a hot coat? Same amount you would use while laminating? Trying to find the best weight/toughness ratio.

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Re: Hot coat hints and tips

Postby TomW » Thu Dec 24, 2020 11:46 pm

Matthijs94 wrote:
Wed Dec 23, 2020 9:12 pm
How much resin do you guys usually use for a hot coat? Same amount you would use while laminating? Trying to find the best weight/toughness ratio.
I use about 25% less than a lamination of same area. A bit drips off.

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Re: Hot coat hints and tips

Postby Matthijs94 » Thu Apr 01, 2021 8:59 am

I just finished my first hot coat. Watched a lot of video's and followed the procedure that TomW wrote in this topic (withouth the degassing). Unfortunately I end up with a lot of dry spots. It is mainly on the painted areas, so I assume these are not completely levelled. Next to that I have some tiny air bubbles all over, although I think I can sand them away. I evenly spreaded out the resin by using a new brush with different stroke angles. It looked perfectly even, no dry spots and no air bubbles. Left it to dry overnight and in the morning the resin wasn't levelled anymore. Anyone knows how to prevent this? Could I just put a new hot coat layer on top to get the dry spots out?
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Re: Hot coat hints and tips

Postby longwhitecloud » Thu Apr 01, 2021 9:36 am

Matthijs94 wrote:
Thu Apr 01, 2021 8:59 am
I just finished my first hot coat. Watched a lot of video's and followed the procedure that TomW wrote in this topic (withouth the degassing). Unfortunately I end up with a lot of dry spots. It is mainly on the painted areas, so I assume these are not completely levelled. Next to that I have some tiny air bubbles all over, although I think I can sand them away. I evenly spreaded out the resin by using a new brush with different stroke angles. It looked perfectly even, no dry spots and no air bubbles. Left it to dry overnight and in the morning the resin wasn't levelled anymore. Anyone knows how to prevent this? Could I just put a new hot coat layer on top to get the dry spots out?
That is odd. What was the ambient temperature and could to feel the mixing cup was warm from the chemical reaction when applied. Epoxy can get a waxy surface. Hot coats are good to do when the previous layer hasn’t fully cured. Interested to hear from others.

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Re: Hot coat hints and tips

Postby Matthijs94 » Thu Apr 01, 2021 10:00 am

The ambient temperature was around 20 degrees celcius. The mixing cup was not warm, I mixed it and the poor it over in another cup and mixed it again. The previous layer is fully cured already. The tiny air bubbles are very limited, I don't care about that. I bet another layer of hot coat can fill the spots? Sand it down a bit more afterwards. I use epoxy super clear https://polyestershoppen.nl/epoxy/epoxy ... r-343.html

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Re: Hot coat hints and tips

Postby longwhitecloud » Thu Apr 01, 2021 1:24 pm

Matthijs94 wrote:
Thu Apr 01, 2021 10:00 am
The ambient temperature was around 20 degrees celcius. The mixing cup was not warm, I mixed it and the poor it over in another cup and mixed it again. The previous layer is fully cured already. The tiny air bubbles are very limited, I don't care about that. I bet another layer of hot coat can fill the spots? Sand it down a bit more afterwards. I use epoxy super clear https://polyestershoppen.nl/epoxy/epoxy ... r-343.html
it seems too viscous... there are heating pads that can help things along once mixed if you are not getting exothermic reaction (or a hair dryer - wear a mask), you dont need much time to paint on a hot coat... (ie worry to much about it going off

some resins are much more viscous than others - there are some super viscous ones used for surfboards

i would contact the brand of epoxy for techincal support - always the best first port of call..

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Re: Hot coat hints and tips

Postby kostantin » Thu Apr 01, 2021 1:46 pm

Matthijs94 wrote:
Thu Apr 01, 2021 8:59 am
I just finished my first hot coat. Watched a lot of video's and followed the procedure that TomW wrote in this topic (withouth the degassing). Unfortunately I end up with a lot of dry spots. It is mainly on the painted areas, so I assume these are not completely levelled. Next to that I have some tiny air bubbles all over, although I think I can sand them away. I evenly spreaded out the resin by using a new brush with different stroke angles. It looked perfectly even, no dry spots and no air bubbles. Left it to dry overnight and in the morning the resin wasn't levelled anymore. Anyone knows how to prevent this? Could I just put a new hot coat layer on top to get the dry spots out?
It is dust from sanding the board. It will give you craters on the board.

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Re: Hot coat hints and tips

Postby downunder » Thu Apr 01, 2021 3:47 pm

Correct,

Not only dust but also not prepped surface. You probably did not use paint prep solution before epoxy.

A lot of factors tho. Nope, new coat will just make it worse.

When u see perfect finish it might be a special epoxy formula. Its hard to compete with this what Tom is using.
There is no universal solution if not everything equal. U need to find what works for you.


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