Aluminite

[paulm]

Alumilite is an American brand name of a polyurethane resin rather than a polyester. What is the difference between polyurethane resin in the USA and here in the UK?
I use polyurethane resin, polyester and epoxy depending on the results I want.
I also use pearlex products as well as UK dyes and powders.
I am at a loss to understand why the craving for an American product, does it mean that we will also need the American mould release instead of the UK ones when using Alumilite in PVC piping?

Its really a case of not knowing what to use Steve. There are several of us starting out casting and we're learning together and without much real prior knowledge so the best source of information is youtube and a lot of people on there use it so thats why its being used. I must say though that I have tried a few different types in block casting but I've only used Alumilite on the blanks in the resin saver moulds as I know its good and don't want to experiment with things that are quite valuable in time and money to make such as some of the stamps and money I've cast. I know I should try other things and will do with some of the CMM's but would you risk getting her stuff wrong? you'd be a brave man

 

[rayf6604]

The instructions are very simple Ray. For the Sierra resin saver mould each pen takes 20ml and I make 4 at a time so I put 40ml of each into a cup, mix it up and pour it in the mould. Wack it into the pressure pot (no need to hurry) and pressure it up. Leave for x amount of hours (I leave mine overnight usually) and Bobs your Auntie.

Does it have to go in a pressure pot Paul or will the air bubbles dissipate without? Obviously care would need to be taken to minimise forming air bubbles in the mixing/pouring

 

[paulm]

Sorry Ray, I don't know, I think others use things like ultrasonic cleaners to vibrate the bubbles up and I did put the cup of resin in a vacuum to get rid of the bubbles before pouring but I really could only say have a go and see.

 

[rayf6604]

Sorry Ray, I don't know, I think others use things like ultrasonic cleaners to vibrate the bubbles up and I did put the cup of resin in a vacuum to get rid of the bubbles before pouring but I really could only say have a go and see.

Yes Paul, we can talk and talk about this but you're right, there comes a point when you just have try it and see

 

[Tephy]

In most things you have to remember we are about 2 yrs behind USA, so they have more experience with casting.
I have trolled an American site and retrieved the following to try to clarify the resin/casting situation.
Note you can put Alumilite in place of Polyurethane if you want, also a slow cure polyurethane is available in the UK as I sometimes use it.
I hope the following helps :

Advantages of Polyurethane:
- Very, very little smell when working and no residual stink (I mean smell)
- Sets faster than Polyester (some say this is a disadvantage)
- Less prone to chip-out (at least for me) when compared to Polyester
- No need to adjust for heat or humidity
- No guessing on the amount of hardener, just mix equal amounts by weight
- It is gentler on your turning tools, band saw, jointer, chop saw, drill bits
- Does not shrink
- Thinner than Polyester so it penetrates better for stabilizing blanks (but then Polyester sets slower so it has more time to penetrate
- You can cast a blank and turn a pen in the same day
- You can work it indoors and WIFE won't complain about the smell

Disadvantages
- More expensive than Polyester
- Shorter open time
- Since it does not shrink if you use PVC as a mold you will need a release agent
- Because its thinner than Polyester it is hard to achieve swirls, colors tent to mix together

Polyester resin:
- Gives me much longer open working time
- Adheres to labels (I was never able to successfully cast a label using )
- Is less expensive
- Is far more flexible when it comes to mixing ratios (you need to measure Polyurethane with a scale)
- Finishes easier (for me)

Things to consider with Polyester:
- It has a strong odor
- Curing is more sensitive to heat/humidity
- It shrinks a bit more than Polyurethane when cured.

I like Polyester for pen blanks. It is thicker than Polyurethane, so it is easier for me to get the swirl patterns that I like. It polishes very well also. The only downside for me is that it is brittle. If you drop your pen the wrong way, you will be replacing it. For that reason I only use Polyurethane for my game call blanks, since calls tend to get more abuse then pens.

 

[Tephy]

Forgot to add if working whith Polyurethane ( Alumilite) you really do need a pressure pot ( I run mine at 50 psi if that helps )

If my mould is too big to go in the pressure pot ( happened twice now ) I secured a small electric motor to the mold and put a small nut/bolt through the pulley on the motor, this caused enough vibration to remove most air bubbles. Mounting the motor to a bit of wood and then mounting the wood on pins/springs you could make a small vibrating table .... just a thought..

 

[billyb_imp]

Thanks Steve, more useful information