Hard finish over epoxy

[Anton]

Hello.

I've finished a nice project, the first in my life: a coffee table with some epoxy art. I've used ClearCast 10 epoxy for the clear coat, let it cure for a week, and tried to actually use it. If I put a glass bottle on it and rib it a bit - it leaves visible, and even touch-sensible marks on it!
They promise scratch resistance, but I'm not sure what it actually means. Did I do something wrong, or is my result expected?

I tried to search for suitable finishes. People recommend polyurethane, but some people say it's the same as epoxy in the end. Will it actually protect the surface from the marks?
Ideally it should be clear and glossy to keep the look of the art table.

Sorry, I'm new, it might be obvious, but after a couple of hours of searching and getting all sort of contraversial answers, I'm begging for help. Thank you!

 

[Droogs]

ClearCast 10 is a casting resin rather than a coating resin. As such it's not really what you should use as your top coating. I'm guessing you are after a really high gloss finish, if so then something like GlassCast 3 or Waterclear both of which you can pour over the stuff you have already. Just pour a very thin layer and allow excess to drip off and denib once cured.
I would also give your clearcast a couple more days to cure a couple of feet away from a radiator in a ventilated room to see how it goes first
hth

edit here's a howto
https://www.youtube.com/watch?v=qQrRVUarzPc

 

[Anton]

Hello, thank you for a quick reply!

Indeed, I've noticed the epoxy type might be wrong, but I didn't know it can make so much difference. I've also used GlassCast 3 on another surface, and after 2 days it also got marks. Now I realize 2 days are not enough at all.

Anyway, even if I follow the advice and do it all right, can I expect zero marks from a usual usage? Or is there a way to improve the surface with some finish, ideally without much gloss and transparency lost?

 

[Droogs]

The resin itself once cured properly is fine for every day usage (water will just sit on top of it and while you will get finger marks etc, they will wipe off) and will polish up very quickly and sparkly. But like all finishes, can be damaged by heat. So still use a coaster or napkin kind of thing but will take lots of knocks etc

 

[Anton]

Ok, thank you!
And about the heat resistance - what if I put a layer of high temp epoxy like EL160 (the first I found)? It seems to have a good hardness and temperature resistance. Looks like it should easily handle hot things put on it for a short time. The underlying coats are far not as resistant, but they should get less heat. They will still heat up and get softer and so on, but be shielded from the mechanical damage by the outer coat.
I understand this EL160 is not completely transparent, but it might be OK for some applications.

I just don't like the idea of coasters

 

[Trainee neophyte]

I don't know if it is relevant, but epoxy surfboards,boats etc are varnished to protect the epoxy fro UV damage. Quite what the effects are from indoor use without protection, I have no idea. It's not as if you will be in the sea, in the tropics, catching gnarly barrels on your coffee table. Or is it?

All in all, epoxy is an amazing substance. A combination of a liquid epoxy resin and hardener creates a chemically inert plastic that can be cast to any shape, used as a filler, glue, or coating of a wide range of mechanical properties. Most important of all, it is a superb bonding agent for high tensile strength fibers and other materials.

There is a weak spot, however. Despite advances in chemistry, epoxy has one big drawback. When exposed to UV (ultraviolet) radiation such as full sun, sooner or later it discolors, turns very brittle, and eventually disintegrates. Adding pigments helps but this is no consolation if you want a clear coated fiberglass over your mahogany deck on a sailboat or a wooden kayak or canoe. A varnish or other coat with UV absorbing additives is the only solution.

Indoors, away from a window, it may be 20 years before you see any sign of discoloration. Or it may not.

 

[Anton]

Most if epoxies claim to be UV stable. Anyway, that's not what I'm concerned with for a coffee table, which will be used indoors, but with quite hot cups slammed on it randomly, so hardness and heat resistance are more important.

 

[Anton]

Let me summarise what I'd like to achieve.
1. Scratch resistance, to the point when I can put a mug on it without worrying to leave marks.
2. Heat resistance, to the point of putting a cup of hot tea and leaving for a few minutes.
3. Ideally keeping the glossy look, with all the nice art still visible.

Is it even possible with epoxy? Any finish I can apply on top to improve it? Maybe even something as weird as a sheet of some clear plastic on top, glued (with epoxy probably) to the surface?
I just don't like coasters at all. I understand the table might need some minor polishing periodically to keep the look, but I'd like to minimize it.

 

[Rich C]

Epoxy might take a couple of weeks to fully harden mechanically.

I'd be inclined to put a coat of high temperature polyurethane over it though as that will have a tougher surface.

 

[Droogs]

This stuff is rather cool to use as coasters and for me, i think it compliments a table, especially as it is only 2mm thick:

https://cork-shop.co.uk/product/rubber- ... ard-2mm-2/

comes in 100mm x 100mm sheets and cuts to shape really easy. also this stuff
https://cork-shop.co.uk/category/cork-wall/

 

[Anton]

No, I don't like the idea of coasters - too much care is required.
I'm currently thinking about an acrylic sheet on top of a table, glued in with epoxy. It seems to be really scratch and heat resistant. Not very good with impact resistance, but it will be securely attached to a hard surface, should be strong enough to survive a mug put on the table with a bit of force, isn't it?

Not sure how easy it would be to put a sheet of acrylic with no bubbles trapped for a 60x60 cm table though.

 

[sammy.se]

I don't think you should give up on the epoxy route just yet.
Check out the Manor Wood YouTube channel - he does a lot of epoxy tables and recently did a clear glass one. He's on Patreon if you need very specific advice on this. But he is generous with his knowledge and brands he uses even on his YouTube channels.