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Forum topic by Davevand posted 12-12-2019 07:31 PM 279 views 0 times favorited 5 replies Add to Favorites Watch
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Davevand

151 posts in 1445 days


12-12-2019 07:31 PM

Topic tags/keywords: question finishing

I am making some serving trays and will be using epoxy for the bottoms.
On my test pour the epoxy ran out of the small spacing in the work piece, will blue painter tape seal well enough to stop this or should I use something else?
Is there a formula that will give me the amount of epoxy I need to cover the bottom to say 1/8 thick, or is it just a guess?


5 replies so far

View John Smith's profile (online now)

John Smith

2135 posts in 771 days


#1 posted 12-12-2019 07:49 PM

for a “guesstimate” for the amount of epoxy, you could line the tray with
aluminum foil or saran wrap and fill with water – measure it.
as for the tape, epoxy has the tendency to stick to painters tape.
vinyl tape works a little better.
if this will be an ongoing project with your epoxy pours, I use a red vinyl tape
made by ShurTape – it is called Stucco Tape. available in most Box Stores.
you can put some mixed epoxy on different tapes that you have to see the results.

I don’t understand what you say about the “gap in the workpiece”.
you have any photos available ??

.

.

-- I am a painter. That's what I do. I paint things --

View John Smith's profile (online now)

John Smith

2135 posts in 771 days


#2 posted 12-12-2019 08:38 PM

and another item I use for all kinds of stuff besides electrical . . . . .

there are dozens of different types of epoxy and tapes.
so when you understand that, you know you will have to experiment
a little with the products that you use to see what works best for you.
some masking tapes work well – some don’t
some cellophane clear tapes, packing tape, scotch tape, etc., the same story.
modeling clay, the type that kids use to play with, also works (most of the time).

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-- I am a painter. That's what I do. I paint things --

View CaptainKlutz's profile

CaptainKlutz

2257 posts in 2103 days


#3 posted 12-13-2019 08:15 AM

Epoxy coverage varies based on uncured density of product used. Most suppliers of laminating, casting, or surface coating epoxies have this data, or a coverage calculator on their web site.
The formula is L(in) X W(in) X D(in) X density (oz/in^3).

When I need seal the bottom of something being epoxied, I use heavy duty clear packaging tape. Not cheap stuff, the thicker stuff that is tough to tear.
If you use a paper tape, or thin plastic tape, it shreds as you attempt to take it off. End up having to scrap lots of little pieces off the surface. The thick stuff will peel off in single sheet. I even use it as compression wrap on top or peel ply when putting epoxy and fiberglass on outside of round tubes. (Don’t ask why)

YMMV

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View wildwoodbybrianjohns's profile (online now)

wildwoodbybrianjohns

712 posts in 156 days


#4 posted 12-13-2019 12:56 PM

One of the problems with tape as a sealer is that when the epoxy is curing, it heats up and that heat affects the bond of the tape.

I have used blue painters tape and had no problems, and I have used the same and had leakage to this or that degree.

Silicone caulk is the best for sealing, but i suppose you cant use it on this project. Or maybe clay, like John said.

Red sheathing tape is what the epoxy pros use. Amazon has it, “Shurtape” is one brand. These sheathing tapes are used for vapor barriers usually. And like Captain mentions, these tapes will not become part of the epoxy, they separate easily.

-- Wildwood by Brian Johns: If you tell the truth, you dont have to remember anything (S. Clemens) Edit: Now where is that darn pencil/ tape measure!

View Rich's profile (online now)

Rich

5147 posts in 1198 days


#5 posted 12-13-2019 06:08 PM

Regarding your question about volume, one cubic inch is roughly 0.55 fluid oz. So for example, if your tray had interior dimensions of 12×15 inches, to achieve a 1/8 inch depth would require 12×15 x 0.125×0.55 fluid ounces. Rounded up, you’re looking at about 12.5 fluid ounces. If it were me, I’d mix a pint to make sure I had plenty.

Keep in mind that, as others have mentioned, curing epoxy gets very hot (exothermic reaction). You can mitigate that by 1) using a slower setting epoxy and 2) not letting it sit in the mixing cup too long. Once it’s poured into a thin layer it will have a large surface area to allow the heat to escape.

And finally, epoxy might not be the best choice. It scratches easily. I have always used pre-cat lacquer. I spray the bottom before it’s attached and hit it with 10 or 12 coats, then wet-sand to the desired sheen.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

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