Resin Questions

I bought an Alumilite kit years ago but never got around to trying it. Lost a small part from a kit that lent itself to onesided casting so decided to copy the undamaged one.

Q1. Is there a shelf life on this stuff? Unopened, opened?

Q2. Is modeling clay OK to use as the mold material to make a small copy?

Q3. I made 3 batches so far. I may be having problems with the proportions as the quantity I need is very small. Seems like more catalyst is better than less. True? In all cases it seemed very thick, as in how the heck would you pour it into a closed mold? Am I doing something wrong, is it to old?

I managed to get a not to sticky mixture on the 3rd try. Dabbed it into the mold and waited for what was in the cup to firm up. I popped it out of the clay mold, it seems to have worked, though still rubbery.

Q4. I put everything away so I would stop dicling with it. How long should it take to really dry hard and be ready to work?

I did warm the bottles in a tub of hot water and mixed and shook the base for quite some time until all the oil seemed to go back in suspension. The catalyst is clear and looks fine. The inner plastic cap on the base was fragile and I had to trash it to get it out. I put some plastic bag material under the screw cap to reseal it it, the catalyst cap was fine.

Thanx Frank

Reply to
Gray Ghost
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If you mixed at the recommended 1:1, it *should* work OK. Using clay as your mold material may have interacted with the resin curing, maybe? I use their mold making RTV for molds. With a 10:1 by weight mixing ratio (mud to catalyst) a digital scale is just about a must to get the correct ratio. Another thing you may want to look into is a visit to your local veterinarian. Most keep the used syringes just for us hobbiests. That is how I get the right dose of resin to catalyst for the parts :-)

-- Chuck Ryan Springfield OH

Reply to
Chuck Ryan

Sounds like a shelf life problem to me. I've had symptoms like what you describe with resin that had been sitting on the shelf for too long.

Rob

Reply to
Rob van Riel

The folks at Alumilite are happy to answer your questions. They have a really good FAQ section on their website. Call or write them, I have always found their staff understanding and helpful.

Reply to
Hawkeye

Yes.

Yes.

Throw it out and order some Smooth-On 300.

You should be able to demold in 20-30 minutes for small parts and it should be fully hard within an hour.

Reply to
Ron Smith

snipped-for-privacy@yahooo.com (Gray Ghost) wrote in news:Xns98D0D2B35C22Wereofftoseethewizrd@216.196.97.131:

Thanks all. Went to Hobby Lobby today and gave the bottle there a shake. Eesh! My stuff is much thicker, obviously toast. Bought the small box for $30 with a 40% off coupon for a total of $18.

Alumilite says 1 year shelf life but didn't specify if they meant before or after opening. Kinda suspected I'd had it to long.

Oh well. I'll make my part and I will have fianlly done it. Gotta couple more things in mind already to dupe to dress up other kits.

Anyone know if the RTV holds up or am I tossing that stuff, too?

Frank

Reply to
Gray Ghost

The RTV I have is just about a year old and is working well, so far :-)

-- Chuck Ryan Springfield OH

Reply to
Chuck Ryan

I've heard (but haven't done it myself) that cold temperatures can extend shelf life. If you have a beverage refrigerator (or a ~very~ patient wife to use the main fridge), you could store it in there. Anyone else hear this or is it an old wives' tale?

Reply to
The Old Man

All chemical reactions are slowed down by lower temperatures, so yes, this will work. How much is another matter; it might extend shelf life by as little as a day, or as much as virtually forever. Keep in mind though that humidity is bad for resin, so if you choose to put it in a fridge, make sure you seal the containers very, very tightly, or the humidity problem may outweigh the low temperature gain.

Rob

Reply to
Rob van Riel

Premixing, as you did, is essential. Personally I have found the recommended mixing ratio to be fine. Make sure not to use an "open" mold, with substantial area open to air. This stuff cures thermally, and any interface open to air does not get quite hot enough in a thin layer at surface, and will stay sticky. Use a full mold. Also, keep molds vertical, so you have some hydrostatic pressure in sprue, and enough vent tubes to let air out of mold (at least one at every local "high spot" in cavity. Sprue should enter cavity from bottom (J- shaped sprue), not top. If resin enters from top of cavity the air in the mold will have to battle the incoming resin to get out.

Reply to
Don Stauffer in Minnesota

The only way to know is to try it. Mix up a small amount in a wax-coated paper cup and see if it cures properly. If it does, you know it's still usable.

I've had resin and RTV last for years, just stored on a shelf in my basement, but they can just as easily go bad in a few months. It depends on the temperature, how tightly it's closed, and the humidity of the air inside the can. Cool is good, moisture is bad. If you open it when the air is humid, try to use the rest within a few months.

Reply to
Wayne C. Morris

snipped-for-privacy@yahooo.com (Gray Ghost) wrote in news:Xns98D0CA35D8CE3Wereofftoseethewizrd@216.196.97.131:

Well now, my part came out fine save for a thin wafer to remove. Looks good, now I have to find some of the items I wanted to duplicate. Not easy considering there may be 40 or more U-Haul boxes full of kits to unpack yet. Guess I'll have to build the shelves first. Dang

Frank

Reply to
Gray Ghost

Urethane resin does have a shelf life. A year is past due. It may still cure but the properties have changed (thick now) when fresh the urethane resins we use to cast detail parts are very thin until it starts to set up. depending on your part size a copy should be ready in an hour or less. Thick parts cure faster due to the heat from the curing resin. Other things besides age that affect these resins are moisture absorption from the atmosphereic humidity and mix ratio being off. The resin I use is more forgiving than Alumalite on this.

HTH, Mike West/Lone Star Models

Reply to
Mike West

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