Hot coat hints and tips

[RichR2]

For years I've used SP115 resin for builds but it is a bit pricey so switched to easy composites EL2. It's fine for laminating but has been a PITA for hot coats. With SP115 I just brushed the board off and perfect finish every time, yet with EL2 it's as if I have a patches wax resist on the board. I've tried acetone, soap and water, never touching the board except with gloved hands, roughing up the surface with 60 grit, 100 grit, 240 grit, temp in workshop is 20C...whatever I do I still cant get a surface without fish eyes of varying sizes. Finishing boards is taking way longer and often requires an extra hot coat/sanding which I hate. Any ideas?

[Trent hink]

Hi, i have used some brands of epoxy that behave similarly. My advice is sand with 80 grit, use a big paint brush to dust it off and don't touch the surface without gloves after sanding/ dusting.

Some epoxies are super sensitive to surface contamination and wiping the surface with solvents will introduce contaminates. If you see a spot or two where fisheyes are developing as you are applying the hotcoat, you can wipe those spots with a clean paper towel and apply more epoxy with reasonably good results.

[TomW]

For years I've used SP115 resin for builds but it is a bit pricey so switched to easy composites EL2. It's fine for laminating but has been a PITA for hot coats. With SP115 I just brushed the board off and perfect finish every time, yet with EL2 it's as if I have a patches wax resist on the board. I've tried acetone, soap and water, never touching the board except with gloved hands, roughing up the surface with 60 grit, 100 grit, 240 grit, temp in workshop is 20C...whatever I do I still cant get a surface without fish eyes of varying sizes. Finishing boards is taking way longer and often requires an extra hot coat/sanding which I hate. Any ideas?

Use easycomposites.co.uk xcr coating epoxy. No blush. I can de-gas it and pour/ brush on and it gives me nearly perfect finish.

[RichR2]

I've just got some, so will give it a go on the next build. How do you de-gas it Tom?

[TomW]

I've just got some, so will give it a go on the next build. How do you de-gas it Tom?

I made a simple one using a thick plastic water jug. Upside down on a board, seal the edge with seal tape, air evac hole in from edge litte hole to that hole in from top. Google it.
Then I mix epoxy in a cup, put it in that chamber for 5 min pounder vacuum.

[alpaia]

Thanks for the tip, so 5 min in vacuum is enough to have nearly no bubbles afterwards in the hot coat ?

[longwhitecloud]

I have heard of glassers hot coating epoxy layups with polyester resin to make things a bit easier and getting a good bond.

[TomW]

Thanks for the tip, so 5 min in vacuum is enough to have nearly no bubbles afterwards in the hot coat ?

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.

[jaros]

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!

[TomW]

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.