I would like to try casting..........

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skiprat

skiprat

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....but I could use some advise please.
I am pretty familiar with pressure and vacuum pumps and the bits and bobs that go with them as I use them for work. I have a very good Dilo set up and have made a tank already.

What I would like to do is cast my part made blanks in resin (probably clear mostly ) An example would be like a pen I made with braided copper cable a while ago, and things like that.

I've read as much as I can find here, but can't decide if there is a particular type of resin I should go for. ( as apposed to brand ) I get confused with all the names like Polyresin, Acrylic resin etc. I think I need the stuff that you guys cast snake skins in. But I don't know what products are the correct ones. I've found several UK site that supply clear resin, but none of them mention if the process is suited to vac or pressure to get rid of bubbles.
They all seem to just mix, pour into mold and wait[?]

All help would be welcome, thanks:D
 
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Most of us use polyester resin, which can be found at Michael's or other craft stores (though there are much less expensive places to get it, too). Some have had good luck using epoxy as a casting medium, and others use Alumilite. All have their advantages and disadvantages, and each is its own formula for a plastic-like compound.

Here is my personal take on each - I've only dabbled in epoxy, and haven't tried Alumilite, so my undertanding may be (and likely is) a bit off, but you've been around long enough to know that about me! [:D]

Polyester Resin - easiest of the three to use. Cures essentially clear ("water clear"). Stinks like crazy. Very prone to bubbles. Some here have had luck using ultrasonics and/or vacuum to degas (i.e. remove the bubbles). Seems to work a little better for textured stuff if you use some pressure, but it isn't necessary. It has a tendency to get fairly hot during the liquid to solid conversion, so you need to be very careful. Although it's the easiest to use (ratios of catalyst to resin can be off by large percentages and you'll still get useable results), it can be finicky in that temperature (and the time you're willing to wait for the resin to set) tends to impact how much catalyst you need. The more catalyst you use, the faster and hotter it cures, but the resulting blanks tend to be brittle.

Epoxy - might actually be a little less expensive than the others. Has a tendency to yellow over time, which may not be a big deal depending on what you're casting. Has to be mixed in fairly controlled ratios, or it won't cure properly. Doesn't stink anywhere near as much as polyester resin. Longer curing times seem to make it less prone to holding onto bubbles.

Alumilite - again, this is what I REMEMBER, and hopefully Curtis or someone else with experience will correct me - cures very clear. More expensive than PR or Epoxy. Not as fussy about the catalyst as PR or Epoxy. Cures hard, but not overly so, such that the blanks can be easily turned. Is not prone to bubbles. Although some use pressure, it isn't as necessary as with PR (which, again, it's not NECESSARY, but it seems to help).

Did that help, or just confuse things
 
The majority of my experience is with Alumilite, a water clear urethane casting resin so that is what I will mainly address. Jim is a little bit off on a couple of thing regarding Alumilite but otherwise pretty close!

Alumilite is certainly more expensive then PR but in most cases is not more expensive than a good quality epoxy. Epoxy is not used that often for casting, though. I also would say that PR is certainly NOT the easiest to use. It is more commonly used mostly due to the lower cost, IMO. PR has a much steeper learning curve since you need to adjust the number of drops of catalyst depending on a number of factors such as thickness of the casting as well as ambient air temp. PR is also much more hazardous to you health since it contains styrene. Read the MSDS for more information.

Alumilite, as well as most urethane casting resins, is a 1:1 mix resin, meaning you use 1 part of A and 1 part of B. The ratios need to be accurate to get the best results and usually is best done by weight. You always use 1:1 and never change the ratio. Simply measure, mix, and pour. The set time is about 10 minutes and you can turn your blanks as soon as 45 minutes after pouring.

Alumilite has very little odor. So little in fact that you could mix and pour at your kitchen table without stinking up the place. The smell was one of the biggest things I despised with PR. I have an air conditioned shop and do not want to have to air it out while or after casting.

Alumilite clear ABSOLUTELY must be vacuum or pressure cast if you want completely clear castings. Otherwise you will have tiny champagne bubbles throughout. The good thing is that you only need to keep it under pressure for 10-15 minutes since that is all it take for the resin to set.

The physical properties of cured Alumilite compared to PR shows that it is a fair amount harder with a Shore D hardness of 81 if I recall correctly vs. 75-78 with PR. The reason Alumilite turns a little easier typically is because it is less brittle. You can make an Alumilite blank and throw it on the floor as hard as you can and it will not break. I have heard of folks cracking PR blanks by simply dropping them but I have no direct experience with this and am going simply on hearsay.

Here is an older document that I found VERY useful when I started casting: http://users.lmi.net/drewid/resin_faq.html

I hope my response at least helped you learn a little about Alumilite resin. I know I may sound biased but I honestly do not own any stock in the company or get paid anything for being their cheerleader! I just really like their product and company and am not afraid to tell everyone!
 
Gentlemen, many thanks for the very informative replies.I'm sure that they have helped others as well.[:D]
If I can find a UK source for Alumilite, then I think I'll try that route first.

One small thing that I forgot to ask, is about shrinkage during the drying setting process. I guess this wouldn't normally be an issue, but I would like to try casting between segments that are already on the tubes, when poured.

Thanks again[:D]
 
Casting between segments is not an issue - I have done it many times with wood and other resins and much prefer this method than trying to glue them. It is also a great way (I think the best way) to do inlays. Just glue the inlay to the tube or build it up a little if too thin, and cast around it. Turn everything down and you have perfect lines between the cast and the inlay.

I really look foward to what you will come up with. I'm a big fan of your designs.
 
Well, I found a UK supplier. I will order some today, if I can get a good price for kids [:D] Gee that stuff isn't cheap is it ?
£35 ( $70 ) for about a litre, delivered[xx(]

Here's a link for any other UK guys that might want to have a go.
I will look for a cheaper source if I like my results.


http://www.nigellawton009.com/AlumiliteTeamPic.html
 
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