I have been using smooth-on casting resin and get an oil surface blush after about a day of curing. Per the suppliers recomendation, have increased the mix time at 3 to 4 minutes. Even with the increased mix time using a transfer of mixing cups, still experience a 10% to 20% reject rate.
I would like some help in reducing the reject rate to zero.
or shuold I be looking to other suppliers with resins that do not have this surface oil migration after curing?

What would you recommend to eliminate this high reject rate.
Your experience and suggestions will be appreciated.

I've got no experience with the Smooth-on product. I have used Alumilite, Bragdon and now have settled with HobbyCast from Freeman....until I find something better,

I've not had that problem with any of the resins I've used and I'm not sure what is causing it with what you're using other than maybe a lousy batch of resin. That does happen,

Are you using a mold release that might be contributing to this problem?

Thank you for the information.
I am now looking at those alternative choices.
Supplier knew right away of this problem and that it may be undermixed that causes the problem - not mold release.

Hmmm...that the supplier knew of the problem right away is not what instills a lot of confidence in the product and that others had had the same experience.

Sounds like it's time for a new resin to me.

Check out the Hobbycast 110 - I think you'll find that the price is at least comparable but I think you'll find that the chemical quality is superior. Freeman which owns the Hobbycast line is a large industrial chemical/resin company. Being a chemist myself, the shipping, packing, and chemical documentation was indicative of another level of profession expertise above a hobby material line.

I also like the longer set up time on the 110; more time for mixing, pouring working into undercuts, details, etc. Takes a lot longer before you can demold, but I've liked the way the parts come out of my molds.

Just ordered the 2 # kit of HobbyCast 110 on line.
will post a report of how it compares

Hope it works out for you!

Is this the right product?
http://www.hobbycast.net/products/hc110urethanecastingresin.htm
Joe

Yup!

Hello-

I have always used the Alumilite product and the Dow Corning RTV rubber for the molds and have had very good luck. How does the HobbyCast product differ?

thanks!

-bob

The Hobbycast product is a subsidiary of Freeman which is an industrial resin manufacturer - not a hooby operation per se.

Differences are that the set-up // cure time was quite a bit longer and allowed one to work it into undercuts and fine details and give time to get bubbles out, etc. Demold time is longer too, but my experience after using 2 different Alumilate products and the Bragdon resin was that I liked this better. The latter 3 set up too fast despiute all the tricks to slow them down.

Ok, it looks a little funky in the bottles but it mixes up nicely and pours clean. and, it has a bit more chemical smell when mixing, but being a chemist it's nothing I have not experienced before and it's nothing to get cranked over either.

I have not really experienced anything significantly different betwen any of the RTV brands that I have used...........yet.

quote:

Originally posted by mwb:

I have not really experienced anything significantly different betwen any of the RTV brands that I have used...........yet.

Are you sure, Martin? You've posted this three times today already! Just kidding.

Vulcan,

I'm just having a lousy day with a lot of uncertainty --> Drs. Heisenberg, Schroedinger, Pauli, De Broglie....not to mention Drs. Howard, Fine and Howard...all came for a visit and you can just imagine the level of quantum flux here in my shop,

I'd draw you a Feymann diagram, but I'm all tied up with this big ball of super string....

I'd be interested in the quantum flux when you get time. Quite an amazing subject!

You'll have to come by for cards after we charge up the flux capacitors - just watch out for Hawking, when he's not bluffing, he's cheating, and he's damned good at both

I promise to take you up on that offer.

Most Polyurethane Polymers have an oil base (diesel oil#2) on some of the cheaper brands it tends to leave a residue after solidifying. Also be careful when sanding this stuff because it can give off Formaldehyde fumes, you could become sterile and grow a third eye.

It's true.


Honest

john P

quote:

Originally posted by John Pignatelli:
Most Polyurethane Polymers have an oil base (diesel oil#2) on some of the cheaper brands it tends to leave a residue after solidifying. Also be careful when sanding this stuff because it can give off Formaldehyde fumes, you could become sterile and grow a third eye.

It's true.

Honest

john P

That's another good reason for using the Hobbycast product - you get a complete MSDS included....a little detail that I forgot to include above.

As for sterility and a 3rd eye - personal experience?

Only time I have problems with a 3rd eye is when I'm listening to Tool in the shop - got to keep prying it open....