So what is the trick with gel promoter?

[redfishsc]

Well, I wish you guys could have seen what I attempted today. My main question is: does gel promoter ALWAY cause a sudden liquid-to-solid in 5 seconds once it begins to act? Regardless of the amount of gel promoter, I don't get a gradual thickening--- I get very quick kickover---- the kickover will happen quicker or slower depending on how much gp and/or catalyst I used.

Now, for your reading pleasure, here is the almost funny mishap I had.

I was trying a multi-layer pour using 3/4 PVC.

I wanted the colors to NOT swirl together but only a little bit. So I added my normal amount of catalyst and 3 drops of gel promoter per ounce. Apparently I shoulda used one or two drops! I had four colors--- I added the catalyst and gel promoter and stirred for about 20 seconds. By the time I stirred the fourth one, the first two had already jell-o-tized and were totally useless. :bulgy-eyes:

So I poured the last two colors together before they goopified on me.

Now I have a large black glob (when I tried to pour it, it plopped out before I could stop it) piled on top of a white glob (I plopped them both together into a cup). I started to throw them out but decided maybe it would become "art" at some point.

 

[dalemcginnis]

Maybe you could try adding the GP to one cup and pour it into the mold then add to the next cup and pour and so on? Never used the stuff so don't know.

I've found when I want mine to set fast all I have to do is mix up a batch after it's sat in my hot garage all day.:biggrin:

 

[redfishsc]

Yup, Dale, I will HAVE to pour them one at a time next time. I'm also going to cut back on my catalyst and gp amounts since it's summer anyhow.

I can't wait to cut the two larger billets I poured successfully (were just two shades of blue poured together) Monday. They looked spectacular right after they had set up, but didn't harden enough to cut on the bandsaw when I had to leave the shop.

 

[dalemcginnis]

Can't wait to see them. That's one of the fun things about casting is discovering how it looks after you turn it. I've had some that I thought looked great till I turned them, then they were kind of plain:frown:. Then I had others I didn't think much of till I turned it and it looked great:biggrin:

 

[Paul Downes]

Redfishsc, I got the gel promoter because of your post, It's all your fault! I have found that by adding only 1 or 2 drops to ONE mix (I have been doing 5-7 oz. mixes per different colors) that there is some control to the overall mixing, or not mixing of the colors. I does seem to gel rather quickly. My first attempt is sitting in the shop and looks like a blue turd on a pink slice of bread! I have been wondering how to use the fiasco in something. I might just crush it up and pour resin over the pieces to salvage it. I would sure like to see a product that sloooowwwwly gels or partly gels so there is good control.

 

[redfishsc]

Lol, Paul, I have a couple of turds from recent disasters!

I actually did get some beautiful castings the other day using the gp----- I made a mold out of corian, fill it with blue w/luster pigment (catalyzed, no gp)--- and then mixed up some green and added gel promoter to IT. Once it began to gel (paying very careful attention) I poured the gelling green into the non-gelling blue. The results are awesome, and I can't wait to get a pen made and pic uploaded.

 

[Glass Scratcher]

I have never used Gel Promoter, but in ordering this new 5 gallon pail I asked Mark at US Composites about it and he commented that Silmar 41 comes promoted with Cobalt Napht(whatever) and does not need it added. To add more could be well- exciting. So if you are going to use it you may want to start by adding only 1/10th of the recommended addition.

 

[Sylvanite]

... Silmar 41 comes promoted with Cobalt Napht(whatever)...

Cobalt Napthanate. It is added to styrene resin to cause it to more quickly from cross-linkages between the polymer molecules. In practice this means two things - a quicker cure, and a shorter shelf-life. Many fiberglass fabricators buy their resin "pre-promoted" because improper storage or handling can result in a big explosion.

I'm a little surprised that Silmar 41 has Cobalt Napthanate in it. Silmar 41 is clear, and Cobalt Napthanate is a dark bluish-green (at least, the raw chemical and the promoted resin I've seen is). Also, the Silmar 41 I've cast hasn't cured nearly as fast as promoted resin I've used. But then, the guy at US Composites should be an expert, and I'm certainly not.

Regards,
Eric

 

[bitshird]

Cobalt Napthanate. It is added to styrene resin to cause it to more quickly from cross-linkages between the polymer molecules. In practice this means two things - a quicker cure, and a shorter shelf-life. Many fiberglass fabricators buy their resin "pre-promoted" because improper storage or handling can result in a big explosion.

I'm a little surprised that Silmar 41 has Cobalt Napthanate in it. Silmar 41 is clear, and Cobalt Napthanate is a dark bluish-green (at least, the raw chemical and the promoted resin I've seen is). Also, the Silmar 41 I've cast hasn't cured nearly as fast as promoted resin I've used. But then, the guy at US Composites should be an expert, and I'm certainly not.

Regards,
Eric

This would explain why the last can I got from US Composites has a slight green tinge, it dries water clear, but a 16 oz batch has just a hint of Blue/green to it right out of the can.