need help with casting clear resins

[trooper]

ive been casting resins for years, so im not new to the subject.

but im having problems with clear resins not curing all the way. ive tried two different epoxies and now im trying polyurethane. they firm up but remain sticky/tacky. my measurements are right on with epoxy, my scale measures to .000 , and ive followed the directions to the letter...so im thinking???

im trying to cast the bubble lens from the texas ins. calculator so the part is small.

according to the directions on the polyurethane i should add more cat. for smaller amounts of resin??? is this right? taking in consideration the size of the amount of resin need to cast a small part like this im using 10 drops of cat.

i was thing heat or lack there of was the issue, so i bought a 1500 btu heater, ive kept the mold at around 80 deg. the whole time....it no difference.



any help from you pro's would be great

 

[Yodajammies]

Optically clear resins usually take a ridiculous amount of time to cure. I've had parts that weren't fully cured for up to ~ a week. Try pouring one and letting it sit for a couple days and see if that doesn't do the trick.

Sounds like your mix ratios are right, so other than just letting it sit for an extended amount of time, I'd make sure everything is being properly mixed (2 cup method), and there are no contaminates in your mix cups or on the tools you're working with.

Or maybe you got a bad batch of material? Who knows.

 

[trooper]

thank you for the reply

i can't see it being a bad batch, ive used three brands of resin.
i always use the 2 cup rule...learned that one early on :lol
i always use new wax free paper cups and new stir sticks (popsicle sticks)

my mold is made from rebound 25. i even tried using a small heater to help it along....no change.

this morning i made another cast, this time i increased the amount of catalist i used, maybe thats the trick

any other suggestions?






jerry