swirling the colors

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mostangrypirate

mostangrypirate

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Joined
Jan 4, 2009
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Location
Palestine, TX.
I finished my 1st PR cast pen today. I wanted to swirl the colors a bit. I waited for 20 minutes before adding the 2nd color, but it still separated. I even toothpicked it after about an hour. On another attempt, I tried waiting a bit longer. it was still soupy, but I found CHUNKS in it that were hardening faster than the rest. I want colors to swirl around without blending or sinking. what to you think I might have done wrong???
 

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A few questions for you. How much catalyst did you use. Did you mix it in well. I usually mix pigments to get the color right and then add the catalyst. If it is cold in the shop it will take much longer for the heat reaction to go. The chunky comment is suspicious for either not enough catalyst or improper mixing. You need to be cautious to not add too much catalyst because this will make your blank brittle. I wait for the resin to start to thicken before stirring the mix. It is a waiting game and sometimes the reaction is relatively fast. You can add a gelling agent but that stuff works fast and you need to use it sparingly. I will sometimes add gelling agent to one color and leave the rest regular.
 
Welcome to the madness!

What brand of PR are you using? How much catalyst did you use? How did you measure it? What temperature were you working at? How much pigment did you add? What type of pigments did you use?

The answers to these questions could help us to determine a possible solution to your problem.
 
From my very limited experience what I've taken out so far is this is about 90% trial and error. I sometimes wish Dawn and Eugene and Charles and Don and a dozen others would collaborate on a book, but then it hits me. This is fun, with all the "goofs" that turn out OK anyway.

Just a word of caution: Don't mix real sand in to try to replicate a granite look. I did, and it wrecked a Proxxon table saw blade. Resin mixed with sand is...cement. That's the only one I've actually damaged something with.

Have fun!

Dale
 
never heard of any gelling agent, where do I get it? as far as mixing, I used a drill and wide stick for over a minute without the catalyst. so I know the color blended, then i added 5 drops per ounce cuz it was 3/4" thick. I only hand stirred that, about like i would beat an egg. the finished product is 3/4" thick but since I am pouring the colors separately, should I use the cat. according to individual thickness?
 
HA HA!! spirit...dont use tiny glass beads either. wrecked a good skew, trying to get a little sparkle:eek:...alot of Q's asked, lets see if I can answer.
PR and colors from artstuf.com...about 75 degrees at the time, plus I hung a lamp about 4 inches over my mold. used aprox 1/4 teaspoon of powder pigment for 3 oz. of resin, with 5 drops 15 drops of catalyst per 3 oz. I went with 5 drops per oz. because once I poured all the colors, it would be about 3/4" thick...forgot the rest of the questions...TEE HEE!!
 
One popular jelling agent, called a jel promoter is cobalt napthalate. It should be available from your supplier if you purchase polyester resin from a real honest to goodness resin company. If you get your resin from Michaels, Hobby Lobby, or other hobby/art stores they probably will not know about such things.

The polyester resins we use are pre-promoted with cobalt so that all we need to add is the MEKP to complete the chemistry. That is why they have a shelf life...they are already starting, albeit very slowly, to harden. This phenominum is called jel time drift. There are different levels of pre-promoted reins polyester resins and the cure time is different on all of them. We speak often of Slimar 41 but I've only heard one other member talk about Silmar 40.

Do some searching on gel or jel promoter, cabalt napthalate, jel time drift or do some digging on some of the resin websites or casting websites to find out lots of information about polyester resin that we never discuss here.

Do a good turn daily!
Don

mostangrypirate said:
never heard of any gelling agent
Click to expand...
 
I have mentioned Silmar 40 several times. It is supposed to be one of Silmars top selling resins, except you can't get it short of 10-55gal drums. It has a higher deformation temp, 170F compared to S41's def temp of 130F. It is supposed to be pretty much the same otherwise. I have been playing phone tag with Silmar (Interplastics) for over a month now...

Gelling Agent can help if you have distinct cure inhibition problems. But I will state again what I was told by Interplastics, S41 is promoted at 3 parts per million, so to follow the instructions on the bottle to add a drop or 2 is more than enough to super promote a gallon of resin. Don't use Gelling Agent with liquid pigments containing Titanium Dioxide. You will end up with a block of resin in a matter of seconds.

One of the problems that persist with everyone is the drops of catalyst. How big are your drops??? If your catalyst states use at 1%, then you can:
1) weigh your volume of resin on a scale and calculate 1% of the weight, then measure out that weight in MEKp on your scale.

2) since the specific gravity of MEKp is 1.15, (close enough to 1 for small castings) then using a simple measure like Metric Ounces, which are 30ml to the ounce, and as you are casting say 3 Moz(Metric Ounces), then you are casting 90ml of resin. 1% of MEKp would be 0.9ml. Which can be dispensed in a syringe. I like to use 0.5% MEKp measured against volume, which in this example would be 0.45ml. I use a 3ml/cc syringe with an 18ga needle that I have ground the tip flat.
 
Adding more catalyst doesn't make resin more brittle (not in my experience) and I've used two different brands of resin. They do react differently from each other though. I wouldn't use a gel promoter, with a larger cast, it creates a lot of heat real fast and cause cracking. There is no need to be technical on the measurement. After doing several casts and trying different amounts of catalyst, you will find a mix that works for you. Your temp., humidity, colorants and even the mold material will effect the outcome.
The method I use, my blanks are on the lathe 57 minutes after pouring them.
 
Glass Scratcher said:
There is always a need to be technical, and to be accurate on measurements as possible, whether it is with casting resins or baking cookies.
Click to expand...

I can see what he's saying, though.. there's so many variables of conditions
that while one caster will use 3 drops per ounce, someone else might use
6 drops. Each person will find their own way.

But being technical give you one HUGE advantage in casting ..

REPEATABILITY!

You can't do any minor tweaks unless you know EXACTLY what you did
before. And following a strict regimen allows you to track results when
changing ONE THING at a time.
 
My measurements are the same each time, within reason. There is absolutely no reason to be exact at 1% as conditions will vary and even if it is not exactly 1%, it will still turn out just fine. No reason to be concerned what size the drop is. The drop will be the same when using the same bottle. If you use US Comp. for your resin, the bottle they give out is the same, so your drops will be the same as my drops. Even with cookies, you can alter the recipe and in some cases is very necessary. Altitude is a big factor when baking. It is all just a guide to get you to a starting point. You use what works for you.
No reason to be technical.
 
The tops of the 6oz bottles of MEKp I have received from US Composites have to be cut. As I don't reuse the bottles- each new one gets a new aperature. So from bottle to bottle the drops are different. One good reason to use direct measurement.

But, I am not trying to convince you.
 
Ok, here's my $0.02 on this:

1) He's fine on amount of MEKP and amount of pigment
While he may not be perfectly repeatable, he's within the
limits of reasonable casting.

2) If I'm reading what he did right, he mixed the 1st color, waited about
20 min then mixed the 2nd color. After about an hour he ran a toothpick through it.
I'm guessing he's well under 70F if he can toothpick it after an hour.

So why'd it separate? Because he didn't have *both* colors gelling at about
the same time. If I can get to them I'll scan and post some blanks I poured
when playing with the Pearl-Ex pigments- I think they're what he's after. I think
that when he talks about "Chunks hardening before the rest", he was hitting pieces
of the 1st color while toothpicking the 2nd.

Timing the gel can be the hardest part of a swirl, especially if you're trying to keep
the colors more distinct (and hence push the timing closer). Some 500W halogen
lights have helped me out of a few cases where things weren't gelling in sync.

I did a recent 6 color pour the size
of a softball that had a clear core and numbers that would be visible from the outside-
and all had to be timed to gel hard enough to work with but still be green enough to
have a chemical bond throughout.
 
I agree with Jason.

I would mix both colors at the same time, wait a few minutes, and then pour one then the other into the mold. I'd then give it a swirl and cross my fingers.
 
sbell111 said:
I agree with Jason.

I would mix both colors at the same time, wait a few minutes, and then pour one then the other into the mold. I'd then give it a swirl and cross my fingers.
Click to expand...
I agree with both Jason and Steve (haha),
Mix your two (or three) colors at nearly the same time .. maybe staggering each color by the time is takes to add catalyst and completely stir Color-ONE, then add MEKP and stir TWO, then THREE, then, in a little while, let the good times roll, mix them all in some creative fashion ..
res.jpg
 
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