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Epoxy - Sinking Pigment

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Forum topic by PaulfromVictor posted 12-15-2019 06:41 PM 281 views 0 times favorited 8 replies Add to Favorites Watch
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PaulfromVictor

230 posts in 3951 days


12-15-2019 06:41 PM

Hi LJ’s

I am making a table and will be doing an epoxy fill 2” deep, in a manner similar to what you see on the river tables being made. I am using the Super Clear 2.0 Liquid Glass for its ability to do a deep pour. I prefer not to change epoxy if possible. I am in for $100 on this stuff. I did a test pour to about .5”. Initially with the pigment added it looked great. As it cures, the pigment sinks and loses the swirl effect. Any thoughts on how I can fix that?

Thanks
Paul


8 replies so far

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Rich

5137 posts in 1195 days


#1 posted 12-15-2019 08:00 PM

That’s a tough one. Your pigment is probably a powder rather than a pure pigment like Mixol. You might get good information from the company you bought the pigment from, so my first suggestion would be to contact them. I know Black Diamond Pigments are made from powdered mica. Based on their photos I see on Instagram, it is possible to keep it in suspension. If you don’t get a response from whomever you bought yours from, try contacting Black Diamond. My guess is they’ll be happy to offer some advice.

Searching for “pigment not staying in suspension in epoxy” provided some results that might be worth reading as well.

Best of luck.

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

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AZWoody

1477 posts in 1829 days


#2 posted 12-15-2019 10:29 PM

Maybe change up how you mix it?

I always add to the resin before adding the hardener. I use trans tint dye though. I mix it thoroughly and then add the hardener. I don’t want to add the hardener and then be up against the gun to make sure the dye is mixed before it starts setting up.

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Kelly

2627 posts in 3549 days


#3 posted 12-15-2019 11:55 PM

No reason you could not do your pour, THEN add the pigment.

I use a lot of 2:1 epoxy and it’s pretty liquid at room temp. For some things, I wait ten or twenty minutes before applying it, so it won’t be quit so liquid.

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bigblockyeti

6182 posts in 2326 days


#4 posted 12-16-2019 03:09 AM

What color are you using? I do most pours in black and I use refill ink for a rubber stamp. A teaspoon of epoxy only needs 2 drops to make it ultra black without messing up the mix.

-- "Lack of effort will result in failure with amazing predictability" - Me

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CaptainKlutz

2225 posts in 2100 days


#5 posted 12-16-2019 03:35 AM

Depends on many factors. This is common problem in world of polymers.

The best way to reduce settling of pigment is by adding a wetting agent to help the pigment stay in dispersed in the fluid. This requires some chemistry knowledge, and is not a DIY fix.

Another common trick is adding a filler to modify the thixotropic properties. Clay is commonly used, but it removes the translucent nature of liquid. You can get fumed silica fillers that are nearly invisible after cure when used in small quantities. West Systems calls it Colloidal Silica.
It is sort of like adding micro sized long stringy fibers into matrix so the pigment/fillers can’t settle as easy. It takes some experimentation to find the right balance to reduce settling, and not lighten the color with white color of silica. It only takes a small amount. Maybe a teaspoon/tablespoon in a quart of resin.
Be sure to wear respirator when handling it. It floats into air, and is dangerous ingested into lungs.

There is a tremendous amount of science in fillers/pigments for epoxy casting. There are so many variations in epoxy available in market, it is hard to supply advice without a couple years using the same brand; which I don’t have.
IMHO – Contact your epoxy supplier, or the epoxy mfg and ask them for solutions.

Best Luck!

PS – Be Safe, Not sorry when working working with hazardous materials!

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

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Lazyman

4502 posts in 1993 days


#6 posted 12-16-2019 04:11 AM

How long did you wait between mixing and pouring? Did you wait to let bubbles from mixing escape first? It seems to me that the same thing that allows the deeper pour (1 hour working time) may also allow the pigment to settle. I’ve used a 30 minute epoxy with no settling problems. I think that the pigment was mica based and bubbles were not as critical for my application. You may have to wait longer before mixing in the pigment, trying to minimize adding any new bubbles while adding the pigment and pouring. Perhaps you can tell from your experiment whether you could wait 20 minutes after mixing resin and hardener to add the pigment, for example, and still have time to complete the pour and still have the bubbles escape. Don’t forget that temperature differences affect the working time.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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HokieKen

11997 posts in 1744 days


#7 posted 12-16-2019 02:10 PM

You might consider doing the pour in consecutive layers with a very thin layer at the top. That way the pigment can’t sink far. Also like others have said, wait a little longer to mix the pigment in and pour. If it has a 15 minute open time, maybe wait 10 minutes, mix your pigment in, let air bubbles work out, then pour it just before your open time winds down.

Another option is to try some food dye. Yes, I’m cheap but it’s always worked well for me.

-- Kenny, SW VA, Go Hokies!!!

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PaulfromVictor

230 posts in 3951 days


#8 posted 12-16-2019 08:21 PM

Thanks for the good responses. I don’t think waiting to add the color is an option. This stuff takes 2 days to cure. I am using copper and gold colors and want it in a clear fill. I will test with different pigments. A final shallow pour or faster cure fill might be an option too. In all the videos people post, people don’t seem to have this problem.

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