Silmar 41 vs Alumilite Clear Slow

[MainelyPens]

Hello all,
I have been using Alumilite Clear Slow for the last couple of years making crushed shell pens with success.
A year or so ago I purchased two gallons and cast, cast, cast, eight blanks at a time building up a good supply for future use.
Last month I grabbed a couple of these blanks and noticed they had turned a light yellow color.
I remember reading post by others here that Silmar 41 produced a clearer end result so I thought I'd give it a try.
Given Silmar is a Polyester and Alumilite a Urethane the first thing I noticed was the odor (wife noticed it as well upstairs).
The Silmar is clearer but the cure time seems days not hours.
Price is another consideration.
After turning a blank to size what little material is left I'm thinking the slight yellow discoloration isn't really noticeable?
What are your thoughts and experiences?
Thanks,
David

 

[Kenny Durrant]

As mentioned here before all resin will yellow over time. The logic with pens is that you turn it so thin it's not that noticeable. Now if it's on white it is noticeable. I've used Clear Slow with a white blank and it looked very old. My buddy said it made it antique. I use both resins and use the one that suits the project. If the shell is white and the yellowing is an issue you might consider tinting the resin to hide the yellowing.

 

[jttheclockman]

Ken said it well. All resins will yellow over time. being we thin the blank so much this does not get noticed much but if you leave a blank that has been clear cast and sits for some time you will notice the yellowing for sure. I have used Silmar for many years and still do on occasion. But if I am clear casting things like watch part blanks I will now only use an epoxy resin and I use Liquid diamonds. This is because epoxy resin sticks to anything. I have had silmar pull away from parts when cured. just my findings. others may differ.

 

[its_virgil]

What are your thoughts and experiences?
Thanks,
David

I have been casting for 20 years, mostly snake skin blanks. Polyester resin and specifically Silmar 41 has been the best choice for casting snake skins. Alumilite Clear and Clear slow have not worked well at all. Epoxies have been hit and miss although others have good success with epoxies. Customers complained about the turning and polishing of epoxy resin. Just my experience. BTW, I have never noticed PR taking days to cure. Cast in the evening and turn the next evening. PR stays sticky on the surface exposed to air and that takes several days to totally dry or one afternoon in the Texas summer sun. The air exposed surface stays tacky because PR is made to be able to pour in layers and the tackiness helps the layers bond.

As for yellowing I have some PR clear cast blanks that are two or three yrs old and they have not yellowed. Epoxy blanks yellow rather quickly even when stored in a drawer having never been exposed to light from any source. Alumilite Clear and Clear slow will yellow but not as fast as epoxies. Those are my thoughts and experiences. Each resin has its good and bad qualities and uses.
Do a good turn daily!
Don