Smooth Cast 300 vs. Smooth Cast 321/320
- Thread starter gaj2714
- Start date
- Status
321 has the longest pot life of all, which is approximately 20 minutes. It can be used in place of Rondo, I believe. It's a little softer than 320, and quite a bit softer than 300, so it's easier to sand. 300 is the hardest and fastest setting. 320 is right in the middle. Also, 320 is supposed to take pigments better than 300. If you're looking to get only one variety, get the 320.
I got the sample kit of 320 and I love it. There's only one problem with it. It's so viscous (almost like water) that you must resin your pieces multiple times in order to get it air-tight, so the Smooth Cast doesn't leak out.
I got the sample kit of 320 and I love it. There's only one problem with it. It's so viscous (almost like water) that you must resin your pieces multiple times in order to get it air-tight, so the Smooth Cast doesn't leak out.
No. 300 cures in about 15 minutes, 320 takes around 1/2 hour, and 321 takes about an hour, I believe.
Brandon McClain
Well-Known Member
Smooth cast 300 and 320 both have the same cure times, demold times, pot life, tensile strength and hardness. 320 is designed to be pigmented, which I highly recommend, it helps you see the layers you are working with. 320 and 321 have the same physical properties, 321 just has a longer pot life and cure time, 7 minute pot life and 20 minute demold times instead of 3 minutes and 10 minutes. Other than pigmenting, I have seen that bondo has a tough time mechanically bonding with 300 sometimes, however I haven't had any issues with bondo and 320. You can find all the info on smooth on's website. I don't know where you guys got your facts, they seem pretty off to me.
Brandon McClain
Well-Known Member
I use a combination of all the different methods. Smooth Cast is the expensive route but is easy. And yes you can lay fiberglass in smoothcast inside. You don't really need to if you go about between 1/8th and 1/4 inch thick inside. Nice thing about the smoothcast is that it's non toxic.
It is toxic, actually. Part A anyways. The MSDS says to use basically the same safety equipment you'd need for polyester resin as well.
Brandon McClain
Well-Known Member
Yeah, but that one covers only part B (note section 1). Part A has a MSDS of its own, you can download both of them in one PDF here: http://www.smooth-on.com/index/view_msds.php?products_id=0146
Here's a quick quote of the interesting parts:
(Comparison: Styrene is rated Xn as well, but has "only" the risk statements R10 (flammable), R20 and R36/38)
(That's basically what most polyester resin and styrene MSDSs say as well.)
Here's a quick quote of the interesting parts:
(Comparison: Styrene is rated Xn as well, but has "only" the risk statements R10 (flammable), R20 and R36/38)
(That's basically what most polyester resin and styrene MSDSs say as well.)
Brandon McClain
Well-Known Member
True, but this relates mostly to ingestion of the product. The vapors are dangerous when breathed in concentration, but when openly exposed disperse into non-dangerous concentration- .005 ppm. The vapors occur in concentration when heated or aerated. In other words, don't stick your nose in the bottle and breath it all day long, and put the lid back on between uses (also prevents spills), and keep at room temperature. It is fine to use indoors if you can ventilate. The reacted materials are also non toxic and don't produce toxic vapors as a by-product of the reaction. So this is what I meant when I said its non toxic.
Anyway, don't want to distract from the purpose of the thread. Be smart when working with these materials. Read the instructions, wear the proper ppe etc.
Anyway, don't want to distract from the purpose of the thread. Be smart when working with these materials. Read the instructions, wear the proper ppe etc.
Attachments
I'm not sure I'm understanding you right. These 0.005 ppm from the MSDS aren't what the vapour disperses into, they are the maximum concentration that is allowed in a workplace environment. They seem really low as well, compared with the limits of other substances.
Sorry for taking this off topic. Maybe a mod could move this portion of the thread into a new thread? I think it's worth talking about.
Sorry for taking this off topic. Maybe a mod could move this portion of the thread into a new thread? I think it's worth talking about.
- Status
