Epoxy air bubbles

[Kerry13709]

Thought I would bring this here so as not to step on Jim's fine looking varnish job.I checked my epoxy sole job this morning and it seems most of the air bubbles made it to the top and popped. I think I should be able to sand it from here for the varnish coat. There are a lot of little craters on the surface from where they burst. Is this normal?

 

[FrankR3878]

several things to try

try tipping out the epoxy with a foam pad and use foam rollers (made for epoxy) to apply it first. Also try to apply epoxy in the cooling part of the day - temperatures falling so that the bubbles don't expand as much.

 

[Kerry13709]

Air bubbles

Frank, to late for that. I have put the three coats recommended on each side. I am looking at getting the teak & holly side smoothed up for varnish/poly coat.

 

[Jim Seamans]

Kerry after sanding

The varnish should take care of any craters or holes- if they are not to big. I would start with a thinned varnish so it flows and penetrates all of the holes.On some larger (2 x 3ft) I have actually pored the epoxy on the piece and used a plastic trowel to spread it round. Then tipped it off with a brush. Jim

 

[Kerry13709]

Tipping off

I guess the tipping off thing is what I missed. I used the rollers from west system to apply the last two coats on the teak side. I thought it was as smooth as possible, so I did not tip off. I thought that was for uneven spots, but I think I was not understanding it right.

 

[John Howitt]

Sand

with a block of hard wood wrapped with 320 grit paper. This will flatten the high spots only. Do not use your hand as this will follow the contours of the finish. Be careful to not sand through the finish ,but if you do, just apply another flatter coat. Thin your varnish as Jim says.Keep repeting the hard block sanding and it can't help but come out flat.

 

[Brian M H23]

Gettin There

Are you using a sanding block? Your sanding looks pretty uneven, and very accentuated in the middle. On a car (polyurethane finish), i'd use 400 grit to take out orange-peel. But you need to use a sanding block- longer is better!!

 

[Kerry13709]

Sanding

I am using one of those hand blocks that the sandpaper fits to either end. When I put pressure on it, it gummed up the epoxy as it came off in little rolls. So, I am applying a slight amount of pressure, wipeing the residue off often, and plan to do it all again with a higher grit paper. I used 100 on this which I think is about as coarse as I dare to go. Really don't want to have to recoat with epoxy if possible. Will varnish cover the dulled finish after sanding?

 

[Ross]

Kerry, you have enough finish on there now to allow you to use a little water wi

buy the waterproof paper, 220 is very fine for intermediate sanding, 180 probably better, 400 grit comes close to polishing. Just enough water to carry the cuttings away for the block, wipe up the excess as you proceed. I often wet sand with water or with paint thinner.

 

[John Howitt]

sand paper

Don't buy cheap paper. Good paper should not clog.100 is far too coarse. If you proceed to the varnish, keep sanding with the hard block. It may take a few more coats than you planned, but will look great.

 

[Kerry13709]

Grit size - quality

OK, I'm not real fluent in sandpaper, as you may be able to tell by now. Outside of price, how can I determine if I am buying a quality paper? From what I have read, I think I will try Ross's suggestion and switch to wet sandpaper. I have been washing the serface with water before I sand. Something about removing the amile wax produced from the curing process. And I will switch back to 180 or 220 grit. I believe 220 is what the varnish manuf. suggests.

 

[Ross]

Kerry, Sandpaper is part of a family of what are called coated abrasives

they are graded by grit size which in turn is determined by standard mesh screens. The coarsest being about 24 and the finest about 600. Above 600 mesh the method for sorting is different. 24 grit is used for removing old finish and leaves deep scratches. Most often 24 grit is used for refinishing floors. after you are done with one grit you proceed to the next finer and remove the scratches left by the former. So your sequence could be 24, 36, 50, 60, 80, 100, 120, 150, 180, 220, 280, 320 400, 600, After the 600 grit most go to the polishing compounds. The manner of gluing the grit to the backing material can be with animal based glue or with water proof adhesives. Naturally if you use waterproof adhesives you want to use water proof paper. The next detail is the material used for the abrasive. These can be flint, garnet, emory, silicon carbide, zircon or diamond. After that you can have a range of surface tratments that improve the ability of the abrasive to not clog. Sanding varinsh is much different than sanding latex paint. I hope that this helps more than it confuses.Edit to add: I left out aluminum oxide. insert that between emory and silicon carbide

 

[Kerry13709]

Sandpaper

Thanks Ross, your explanation only adds to my knowledge base , and is appreciated. I will use this to research a little before buying more sandpaper.

 

[Ross]

Don't be afraid to buy the best, Norton, Behr, and

3M will never disappoint.

 

[Brian M H23]

Oh yes - wet sanding

I didn't even think to mention that! But when sanding anything waterproof, by all means keep the surface wet and dunk the whole sanding block in water to wash off residues.

 

[Kerry13709]

Pros and Cons on

the ready made sanding blocks I see in the stores. Are these worth the money, or am I better off getting the sheets and using plastic block?

 

[Ross]

I just use what ever block of wood is close at hand.

Choose one that is 1/3rd or 1/4th the width or length of the sheet.

 

[Kerry13709]

Sanding blocks

No, I mean the type that is pre-made into a block with adhesive on four sides.

 

[Ross]

Kerry you mean the spongey sort?

I use those when I am not concerned with flat just with smooth. They are great for sanding solid wood door before varnishing.

 

[Kerry13709]

Sandpaper

I guess you could call them that. I have some that are sponge with sandpaper on one side. The ones I am talking about are somewhat harder than sponge.I guess what I need is a hard piece of wood, unless the normal hand sanders will work.