Turning Alumilite

[ed4copies]

In this thread: Plastic?

the question was asked, how are the numerous types of plastic blanks different from each other. I gave a short (possibly terse) answer and I was surprised how much interest the thread got.

Our new librarian (and one of my good friends), Wayne suggested that we try to get answers that were "library-worthy" and incorporate this as an article. Honestly, I think that is such a good idea that I am starting a few of these threads and I will incorporate the information into an article for Exotics and make it available to the IAP Library.

Next is Alumilite

Alumilite is a trade name that is frequently used on IAP. I'm sure there are members who can tell us the "generic" term, similar to the term "polyester resin". I hope someone will do that, please (Curtis or Bruce??)

Alumilite is similar to a well made Polyester resin. The "mix" of the two parts is set at a 1:1 ratio, which seems to create a very uniform product, that is easy to turn. Most of my experience with Alumilite is the clear product, so anyone who knows the black or white, please tell us the differences!!

Alumilite does not take QUITE the shine of Polyresin, but it also does not shrink while curing, so it is the better choice for mixing with other media, like wood (worthless wood).

Again, I welcome additional comments!!

 

[Sylvanite]

The various types of Alumilite are urethane resins (as opposed to the polyester, vinylester, and epoxy resins). I've used Clear, White, and RC3 Black. All of them are far less brittle than PR. I don't worry about dropping an alumilite blank.

I find the Clear to be equivalent to acrylic in terms of ease of turning. A full gloss shine can be achieved, but it is more difficult than with acrylic or PR. I have, at times, put a CA finish over Alumilite Clear just for the shine.

Alumilite White and RC3 Black, however, turn very easily (easier than acrylic in my opinion) and polish very easily. Of all the plastics, they are my favorites to turn. They also tap and thread well, and produce strong, durable threads. Alumilite Black and Ebonite are the materials of choice for grip sections on kitless fountain pens.

Alumilite Clear sets much quicker than PR, so it produces good color separation on multi-color blanks. It's more viscous than PR, however, so it must be cured under pressure to avoid bubbles. Mica powders or Alumilite dyes may be used as colorants. Dyes made for PR are incompatible. Avoid moisture or Alumilite Clear will foam.

Alumilite White and RC3 Black are opaque and thinner than PR. They set up very quickly when mixed (about 3 minutes) so have your mold ready before you combine the parts. It's hard to judge colors when mixing Alumilite White. The resin starts out clear but turns white when it sets. Mica powders don't work well (because the resin is opaque), but the Alumilite dyes do. Again, avoid moisture or the resin will foam.

Alumilite has very little odor and the fumes are (supposedly) not toxic.

The downside to Alumilite is the price. It's at least 50% more expensive than Silmar 41.

I hope that helps,
Eric

 

[Ed McDonnell]

Urethane Resins are very sensitive to moisture, which will make it foam. When used with wood, the wood must be absolutely dry. Anything you put in the resin must be absolutely dry. If you live in an area with elevated humidity and work without A/C you may find urethane resins to be a challenge (unless you have better luck than me).

Machinability of cured urethane resins and the short pot life make them worth the hassle and expense for some applications.

In my experience, urethane resins are not suitable for rotocasting because of the short pot life. Although I have not tried the new "Amazing Clear" from Alumilite which has a 45 minute pot life (way longer than their other resins which are 5 - 7 minutes), the 24 hour demold time makes me think it also would not be ideal for rotocasting.

MSDS for the various alumilite resins are available on their website.

Ed

 

[reedrew]

I find it difficult not to get bubbles in the pour...any suggestions???

 

[ed4copies]

Excellent input here!! Thanks to those who took the time to comment!!!

 

[Russianwolf]

mixing is by weight, not volume. And is pretty finicky for smaller amounts.

My experience at least.

 

[Sylvanite]

mixing is by weight, not volume. And is pretty finicky for smaller amounts.

For Alumilite Clear, the A and B sides are different densities, so they must be mixed by weight, not by volume. I normally pour at least 3 blanks at a time, and usually just three colors, so I'm not mixing really small amounts. I can see that if you wanted to pour just one 3-color blank, then getting the ratios right could be problematic.

Alumilite White and Black sides A and B have close enough densities that they can be measured by either weight or volume. I think they may also be more forgiving about ratios.

For all three resins, the dyes are made to mix with the A side, so put all the colorants (dyes and powders) in the A side, stir, and then mix in the B side. For Alumilite White, you can also mix, pour, and then swirl in streaks of color by dipping a toothpick in the dye and dragging it through the mold.

I hope that helps,
Eric

 

[Sylvanite]

I find it difficult not to get bubbles in the pour...any suggestions???

Alumilite Clear needs to be cast under pressure (at least 40psi, I generally cast at 50-60psi). That collapses the bubbles to microscopic size. Alumilite White and RC3 Black can supposedly be cast without pressure, but I use pressure anyway.

Regards,
Eric

 

[1080Wayne]

Alumilite Clear B side tends to develop a hard layer on the surface when in the can for an extended (6months-1year) time . They told me it was caused by storage at too cold a temperature , and could be re-mixed by heating , but I have never tried . For the record , my shop is at 65-80 year round , so I assume cold is defined as anything less than a Texas summer day .

The cans are a PIA to pour small quantities from , so I transfer the A side to a water jug with a spigot tap which allows control to a gram or two . It is not possible for me to do this with the B side because of the hardening problem .

In my opinion , Alumilite Clear is much more forgiving to turn than any type of acrylic or PR . It seems to be un-chippable , even with dull tools , not that I would recommend their use .

Alumilite Clear at 12000 Micromesh will be glossy , but definitely not at the level of most acrylics or polyesters . I always use CA over top and have not had any bonding issues .

Castings can be removed from the mold in about 4 hours bit they will be sticky to the touch . I wait at least 2 days before turning . I suspect full cure takes a bit longer . Additives other than the afore mentioned moisture can accelerate or delay cure . I make one product that I won`t touch for about 2 weeks because of delayed cure . However , the ones that accelerate cure get sworn at the most .

Wayne

 

[MesquiteMan]

Castings can be removed from the mold in about 4 hours bit they will be sticky to the touch .

Wayne

If you are having to wait 4 hours to demold and they are sticky to the touch, something is wrong. I demold as soon as they cool down and never have them be sticky at all. It is usually 30-40 minutes before I demold and that is even in the winter time in a non-heated shop. Granted it is usually no less than 55-60 degrees but it is still not hot. I would double check your mixing methods and ratios as it should never be sticky to the touch after 4 hours.

 

[crabcreekind]

I found that at first alumilite would not shine as good as pr or acrylic. but, after watching Curtis's video for alumilite when he just used a skew and went straight to micro mesh. I tried that and it worked. But you have to have a really sharp skew, and be really good at it (which I'm not) so it would probably be less time for me to CA finish it, than it would for me to do another pen, because I messed up with the skew.
I have never had a problem with alumilite foaming because of moisture. I do live in a desert though. But i wanted to see this "foaming" and mixed a tiny amount of alumilite with water. It didnt foam too bad, and it seemed if there would have been pressure it probably would have negated the bubbles.

 

[1080Wayne]

Castings can be removed from the mold in about 4 hours bit they will be sticky to the touch .

Wayne

If you are having to wait 4 hours to demold and they are sticky to the touch, something is wrong. I demold as soon as they cool down and never have them be sticky at all. It is usually 30-40 minutes before I demold and that is even in the winter time in a non-heated shop. Granted it is usually no less than 55-60 degrees but it is still not hot. I would double check your mixing methods and ratios as it should never be sticky to the touch after 4 hours.

Curtis

Don`t think I have been guilty too often of poor mixing , but certainly have on ratios as for several years I didn`t weigh A & B . I generally cast individual blanks with cracks/worm holes/near total decay and other high value stuff , using duct tape around the blank as the mold . It is possible that the adhesive plays a part in the stickiness . I guess the other caution that should be made is that any additive which delays cure also must delay demold time , otherwise bubble voids will definitely be present .

Wayne