Silmar 41 vs. Alumilite

[Hippie3180]

I'm still struggling a bit with internal polishing, it seems that with Alumilite I can get to about 3/4 of the way…fairly clear but often with a scratch or two I can't get out.

I ordered a small bit of Silmar 41 to see if there may be some better results. I understand there are some materials that accept internal polishing better than others. Anyone have input on this?

 

[JohnU]

Silmar is a harder resin and will polish easier but it's not ideal for threading or kitless. It's just too hard for that kind of working and will break or chip. I personally like finishing Silmar and always get a better/ shinier/ clearer finish than I do with alumilite or epoxy. With this I have to add a CA finish to get the same results.

 

[jrista]

I'd be curious to hear @jttheclockman 's opinion on Silmar. He doesn't like Alumilite (although I think its fine), but apparently he's used Silmar 41 a lot.

 

[NJturner]

I'm still struggling a bit with internal polishing, it seems that with Alumilite I can get to about 3/4 of the way…fairly clear but often with a scratch or two I can't get out.

I ordered a small bit of Silmar 41 to see if there may be some better results. I understand there are some materials that accept internal polishing better than

I have not used Silmar, but I do find with Alumilite it does require a complete sanding process before attempting polishing. I've added some finer grit papers to my process as well as some liquid sanding and polishing to get it to go to a better shine. My only suggestion is if you have a scratch, more sanding normally will not help unless you go down a courser grit or two until the scratch is resolved, and then start back up the grits. Lateral sanding as well as sanding as it spins also helps, since the paper is hitting the surface from different directions and angles. I am testing some new polishing pastes that also seem to cut down on the work while delivering pretty nice results.

One thing for certain is I had to change my sanding and polishing processes that I used for CA finishes when I started using Alumilite materials. The CA just seemed to come to a shine quicker and require much less polishing than I am having to do with the Alumilite. Not sure if Silmar will get you there, but I hear it smells pretty badly when using it compared to Alumilite.

Kevin

 

[jrista]

One thing about urethane (i.e. alumilite) is that it is more like rubber than plastic or acrylic. I think that is why its often harder to "polish", as its not really a hard material, and the nature of its chemical structure is different. I took a cue from John U a while back to use the GluBoost ultra thin as a finish. I haven't done much with that, but I'm going to be making some kitchen utensil handles soon here, and I'll share some photos of the results with the ultra thin (green label) GB on alumilite.

 

[jttheclockman]

I'd be curious to hear @jttheclockman 's opinion on Silmar. He doesn't like Alumilite (although I think its fine), but apparently he's used Silmar 41 a lot.

Ok here is my opinion but first must clear something up. When we talk Silmar resin or at least when I do it is clear Silmar41 casting resin which is a polyester resin. There are other Silmar resins so when you say you got a small batch I wonder where did you get a small batch from. Next I never used any of the Alumilite products. I never will. They are way too finicky from all that I read here. I do not need to add outside problems when casting. I do have a couple gallons I got from another pen turner from years ago but it is probably useless no and probably an older formula anyway. I have no intention of using it.

Next I can not speak to using for kitless and threading. Trust John U for that or others. But I can speak to polishing and can speak about epoxy resin. I disagree with John on polishing disparity between Epoxy and Silmar. I use Liquid Diamonds epoxy resin and I can polish to a high shine as well as the Silmar. The Silmar is a harder resin for sure because you can make it so by adding more catalyst. You can not do that with epoxy resin or at least with LD. It is a straight 2 to 1 mix. I have never used CA on a cast blank weather epoxy or Silmar. Now if there is a mixture of wood in the blank then sure I did. Silmar has a strong odor but never bother me because my shop is in the basement and basically after I mix and pour the resin it goes in the pot. The remaining small amount hardens quickly and is a non smell factor. I do not have any allergies working with either. Epoxy is not as strong a smell and that is good because it has a lot longer open time which is need for what I do.

This probably not what you are asking but was asked to reply.

 

[jrista]

I'm still struggling a bit with internal polishing, it seems that with Alumilite I can get to about 3/4 of the way…fairly clear but often with a scratch or two I can't get out.

I suspect this is because its a urethane. One, I would be careful about starting at lower grits. I NEVER use 150/180, 220/240, 320 on any resins. I am sometimes even wary of 400 grit. The lower grits will leave significant scratching and often deep scratches that can be all but impossible to get out entirely. Starting at 400 or 600 grit, on any resin, it usually ends up being a lot easier to polish things out. You may just need to spend more time at 400/600. Remember also to never skip grits. Its 50% scale reduction each grit, meaning as you progress through the grits, each one will reduce the scratch scale by half. You will often need to sand up to very high grits with most resins, and I will usually sand with Norton wet/dry (wet of course) up through 1500 or so, then switch over to Zona paper starting two grits finer than the lowest (i.e. skip green and gray) and wet sand all the way through 1 micron. That is still usually NOT enough for any resin I've ever worked with, and it usually takes buffing to really shine things up.

Urethane is a bit of a different beast, as its more rubbery in nature. As such, it doesn't naturally want to take on a shine with sanding. It can, but it doesn't really want to. John U recommended finishing Urethane resins (i.e. Alumilite) with GluBoost Ultra Thin (the new stuff, green bottle) as its highly penetrating and will easily flow into every nook and cranny you have in the surface of a urethane blank. You might need to build up a few thin layers. then you an polish that out to a fine shine, like any other gluboost finished blank.

 

[Hippie3180]

I suspect this is because its a urethane. One, I would be careful about starting at lower grits. I NEVER use 150/180, 220/240, 320 on any resins. I am sometimes even wary of 400 grit. The lower grits will leave significant scratching and often deep scratches that can be all but impossible to get out entirely. Starting at 400 or 600 grit, on any resin, it usually ends up being a lot easier to polish things out. You may just need to spend more time at 400/600. Remember also to never skip grits. Its 50% scale reduction each grit, meaning as you progress through the grits, each one will reduce the scratch scale by half. You will often need to sand up to very high grits with most resins, and I will usually sand with Norton wet/dry (wet of course) up through 1500 or so, then switch over to Zona paper starting two grits finer than the lowest (i.e. skip green and gray) and wet sand all the way through 1 micron. That is still usually NOT enough for any resin I've ever worked with, and it usually takes buffing to really shine things up.

Urethane is a bit of a different beast, as its more rubbery in nature. As such, it doesn't naturally want to take on a shine with sanding. It can, but it doesn't really want to. John U recommended finishing Urethane resins (i.e. Alumilite) with GluBoost Ultra Thin (the new stuff, green bottle) as its highly penetrating and will easily flow into every nook and cranny you have in the surface of a urethane blank. You might need to build up a few thin layers. then you a polish that out to a fine shine, like any other gluboost finished blank.

Helpful information. I do very well on the outside, but struggle with the internals, I will take this tips to heart and give it a try. I don't always Glu Boost to get a nice external polish, but do on occasion.Thank you.

I know you do some demonstrators, are you able to get Alumilite totally clear or do you tend to use something harder like "acrylic" when you want to do internal polishing? I've read that "acrylic" is easier to get crystal clear?

 

[JohnU]

Something to remember, urethanes and epoxies are a softer resin so even if you get them to shine without CA, they will dull easier with normal use. CA adds a hard (more durable) surface similar to a car with a clear coat over the paint.

 

[Hippie3180]

Something to remember, urethanes and epoxies are a softer resin so even if you get them to shine without CA, they will dull easier with normal use. CA adds a hard (more durable) surface similar to a car with a clear coat over the paint.

Gotcha, makes sense!

 

[jttheclockman]

Something to remember, urethanes and epoxies are a softer resin so even if you get them to shine without CA, they will dull easier with normal use. CA adds a hard (more durable) surface similar to a car with a clear coat over the paint.

One thing to add to this is that you now have 2 surfaces to contend with for scratches. Have scratches under CA will drive you nuts because not you are thinking they are in the CA. This goes for when putting a CA on wood as well. Just wanted to bring this up so that no one thinks you are getting away with anything for sanding scratches out.

 

[jrista]

Helpful information. I do very well on the outside, but struggle with the internals, I will take this tips to heart and give it a try. I don't always Glu Boost to get a nice external polish, but do on occasion.Thank you.

I know you do some demonstrators, are you able to get Alumilite totally clear or do you tend to use something harder like "acrylic" when you want to do internal polishing? I've read that "acrylic" is easier to get crystal clear?

In my experience, which compared to some here is rather limited, acrylic is one of the easiest materials to work. It take a polish really well, and it can get extremely clear. I guess I would say, inlace, which is more brittle, produces an even clearer shine and if you want something crystal clear, then it might be better...but, its harder to turn, and I suspect (don't have direct experience here) that it wouldn't handle threading nearly as well as acrylic. Poly takes an extremely good shine as well.

I used to just use various plastic polishes in the past, but these days I find that to get a truly crystal clear finish, on anything, buffing is the best way. Even if you start with a plastic polish, which can help, in the end to get the best shine possible, I'd say buffing is a necessity. Now, you mention internal. I am assuming that is the inside surface of a kitless pen? For that, you might want to see if you could find, or even craft yourself, some kind of buffing utility on a small rod, that could be inserted into the pen, to buff from the inside. In fact, some time back, I think someone shared a video of a pen manufacturer that had some contraptions for their lathes that supported this kind of internal buffing. It was done on the lathe, with the buffer held in the tailstock, so that there was little chance of catching and screwing up the pen. (Sorry, can't recall when, or who, or where that was shared...or what the name of the company was... Such is the life of a perpetual insomniac.)

 

[JohnU]

One thing to add to this is that you now have 2 surfaces to contend with for scratches. Have scratches under CA will drive you nuts because not you are thinking they are in the CA. This goes for when putting a CA on wood as well. Just wanted to bring this up so that no one thinks you are getting away with anything for sanding scratches out.

Very true… that's why I use ultra thin CA like Gluboost for the first few coats before switching to thin or medium. It helps fill in the smaller scratches so they aren't visible under the final finish.

 

[Hippie3180]

Very true… that's why I use ultra thin CA like Gluboost for the first few coats before switching to thin or medium. It helps fill in the smaller scratches so they aren't visible under the final finish.

Very true… that's why I use ultra thin CA like Gluboost for the first few coats before switching to thin or medium. It helps fill in the smaller scratches so they aren't visible under the final finish.

How do you recommend getting even application of ultra thin inside a body/cap?

 

[JohnU]

I would apply a couple drops and tip the tube so it rolls over the surface. Let the excess run out of the open end. Use a little and do it a couple times.

 

[Hippie3180]

I would apply a couple drops and tip the tube so it rolls over the surface. Let the excess run out of the open end. Use a little and do it a couple times.

That's how I was applying it, sometimes I get it a bit uneven though. Practice.

 

[Sylvanite]

"Silmar 41" is a specific pre-promoted clear polyester casting resin. "Alumilite" is the brand name of a variety of urethane and epoxy resins. Saying "Silmar 41 vs. Alumilite" is kind of like saying "Corvette vs. Ford".

In general, polyester resin blanks are harder than urethane resin blanks and therefore tend to be easier to polish. There is a wide variety of products, however, so that generalization is not always true. Urethane, for example, can be made into foam, rubber, paint, or hard plastic.

I have cast my own blanks using Silmar 41, Alumilite Clear, Alumilite White, and Alumilite RC3 Black - all with good success. Silmar 41 is polyester; the three Alumilite resins are urethane. When doing demos, I'd sometimes drop a Silmar 41 pen blank on a concrete floor and it would chip or shatter. I'd then throw an Alumilite Clear blank at the floor, and it would simply bounce around the room without breaking.

When I first started using Alumilite Clear, I ran into the same polishing problems as everyone else. The sanding/polishing process that yielded high gloss on acrylic or polyester simply didn't produce a nice shine on the urethane material. I resorted to the same solution as well - I put on a CA topcoat. As my buffing skills improved, however, I found that to be unnecessary. I can get a high gloss finish on all of the urethanes I use (including RC3 Black). I no longer put CA on urethane unless the blank contains an imbedded material that needs it.

I buff acrylic, polyester, and CA-finished blanks with Tripoli and White Diamond compounds. That yields a nice shine. With the urethanes, however, I also buff with blue compound and then with a plain Canton Flannel wheel. That gives me a glass-like shine even on RC3 Black. A light touch is needed as it is possible to buff ridges into the blank if you press too hard against the wheel.

I hope that helps,
Eric