Timing the mixing of different colors

[BCnabe]

After about a year of other home projects I'm finally able to start doing some castings again.

I did a couple batches last night and remembered one of the frustrations I had in the past.

I'm doing castings with 2-3 different colors. I usually pour in the main color and then let that start to set while mixing the other color(s). I keep an eye on the main color to see when it starts to gel.

What I've experienced though is that the top layer gels but underneath is still in a liquid state. When I pour in the highlight/secondary colors it will set on top of the gel layer and when I use a wire to swirl them I almost have to tear the gel layer to get it to go deeper into the mold. But since the resin under the gel layer is still liquid the colors seem to blend together more than I like. I want the colors to be a little more defined/separated from each other.

I had one batch last year that I tried swirling before it gelled and it ended up looking like river bottom mud.

I know there's a very small window of time to do the swirl but is there a way to get the resin to gel more consistently from top to bottom rather than the "layers" I'm getting now? I'm using Silmar 41 with 7 drops of mekp per ounce.

 

[Ed McDonnell]

Hi Dennis - I mix and catalyze all my resin colors for a pour pretty much at the same time (silmar 41).

When the resin is the correct consistency, I will alternate color pours in the mold and then swirl (with a rotating and vertical movement of my swirl stick). This gives me pretty good color distribution through out most of the blank. The very bottom usually stays dominantly the first color I pour. Making that first pour smaller diminishes this effect, but when you know the resin is getting ready to kick it takes a lot of self control to do a lot of tiny pours into the mold.

When pouring in the mold, letting the resin run down the side of the mold versus pouring straight to the bottom can give some interesting results.

I don't do much with block molds, but waiting to add the heavier colors until just before the resin starts to kick keeps them from sinking to the bottom and allows me to work in an interesting pattern.

That's just the way I do it.

Ed

 

[CrimsonKeel]

Some thing to try is pouring the thicker gelled material into the thinner material instead of the other way around.

 

[TimS124]

Another thing to consider trying is pouring the second color from a greater height. It will have more momentum when it hits the color that's already in the mold and it will be a thinner stream...that should let it penetrate deeper vs. just sitting on top. You don't have to get crazy (no ladders needed)...just the difference between pouring close to the top of the mold vs. holding the cup a foot or two above the mold makes a big difference in stream size, speed, etc.

I've been wrestling with the opposite problem...second color seems to sink quickly to the bottom as I pour it in. So, I've been working on things to rob the stream of its momentum (stir stick just above the surface that the stream hits, losing its speed, then dribbles off that stick).

If you find something that works for you, please post the details.