# Alumilite or Silmar 41 for casting?



## healeydays

OK folks,

I am going to do some casting of pen blanks, bottle stoppers and knife scales and am looking at what casting resin most like to use when using the pressure method. The two I hear most about are Alumilite or Silmar 41 for casting and Pearlex and Alumilite for tinting. I'd love to hear what folks think and where are the best places to get a reasonable price for whichever?

Mike B


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## hobbit-hut

I'm glad you posted that. Look forward to hearing about your new adventure.


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## healeydays

So now that Christmas has passed, I thought I'd try this again. Does anyone prefer one over the other? Is anyone willing to share dye color secrets?


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## NYWoodturner

I have cast with Silmar and have no complaints. I have never cast with Alumilite. My casting experience is very limited, so I won't even pretend I know what I'm doing. Curtis Seebeck with TurnTex Woods (I believe he is a member here) has a good comparison video on Youtube.

[video=youtube]http://youtu.be/DvQNK2RXd3A[/video]

I would reach out to him if you have any questions he doesn't answer here.


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## healeydays

Curtis and I have talked about a number of things. Just want to hear anyone else out there doing it too as we do have a wealth of knowledge here and I'm just trying to mine some of it for prosperity...


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## hobbit-hut

I have seen people make statements somewhere that they do both vac. and presure. They made it sound as if they were using the same chamber for both. I don't see that could not be done. If the chamber will hold presure why would it not hold vacume. Later if you wanted to get a vac, pump I would think it could be modified to do both. :i_dunno: really :i_dunno:


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## healeydays

I'm setting up separate systems with a pump that can handle both. I am setting up a pressure system for casting and a tube system for vacuum to be used for stabilization. I am at the stage deciding which way I am going with resins for each process as I have heard comments that folks like both stabilization products and both casting products.


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## hobbit-hut

healeydays said:


> I'm setting up separate systems with a pump that can handle both. I am setting up a pressure system for casting and a tube system for vacuum to be used for stabilization. I am at the stage deciding which way I am going with resins for each process as I have heard comments that folks like both stabilization products and both casting products.



Is there much difference in price ?


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## healeydays

NYWoodturner said:


> I have cast with Silmar and have no complaints. I have never cast with Alumilite. My casting experience is very limited, so I won't even pretend I know what I'm doing. Curtis Seebeck with TurnTex Woods (I believe he is a member here) has a good comparison video on Youtube.
> 
> [video=youtube]http://youtu.be/DvQNK2RXd3A[/video]
> 
> I would reach out to him if you have any questions he doesn't answer here.



That video shows some of the properties of Alumilite that show it's durability. I like that, but he never mentions the brand of the other but I can't blame him as it would be issues for him with that manufacturer.


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## healeydays

Here are comments that were made elsewhere by Curtis. Thought I would share here too.

Here is my take on the subject. I am very pro Alumilite and am one of the first on this site to use it regularly. I tried a number of different resins when I was perfecting the cactus pen blanks. I used PR, Epoxy, and Alumilite and Alumilite has been my choice ever since.

1. Alumilite has virtually NO odor. You only really smell it when you have your face right over you mixing container. You could very easily mix and cast in your Kitchen if your significant other would let you! PR will surely get you kicked out of the house. It is a very strong odor that for me seemed to linger. Also when drilling a finished blank, the PR blank will stink while the Alumilite blank does not.

2. Alumilite runs around $160 per 2 gallon kit. That is 2 gallons of mixed resin so the price is $80 per gallon unless you buy it in quantity like I do and then your cost is only $55 per gallon. PR is certainly cheaper at a little more than 1/2 the cost.

3. Alumilite can be shipped without any hazardous material fees, no matter how much you ship. It is considered non toxic whereas PR is listed by the IARC (International Agency on Cancer Research) as possibly carcinogenic.

4. PR is highly flammable. Alumilite must be preheated before it will ignite.

5. Alumilite is a 2 part system, equal part of A and B by weight. There are no drops to count and you do not vary anything due to environmental conditions or mass of casting. It does not matter if you shop is hot or cold, Alumilite still works just fine.

6. Alumilite blanks are not brittle at all. I had a pr blank that had the tubes installed. I accidentally dropped it on the floor and it cracked. It was a blank made by one of the pro PR guys that says PR is not brittle if done right. Alumilite will not crack if you throw it on the floor! It is virtually impossible to blow up an Alumilite blank while turning. I have taken a blank while square and really jabbed a gouge into it to see what happens. It just turns away and does not give the shattered glass look.

7. The Alumilite Corporation is an AWESOME company to work with and buy from. Alumilite is made in the USA in Kalamazoo, MI. I am not sure if Silmar is US or not?


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## TurnTex

hobbit-hut said:


> I have seen people make statements somewhere that they do both vac. and presure. They made it sound as if they were using the same chamber for both. I don't see that could not be done. If the chamber will hold presure why would it not hold vacume. Later if you wanted to get a vac, pump I would think it could be modified to do both. :i_dunno: really :i_dunno:



Vacuum for casting is not the best option, IMO, especially if you are embeding anything in the resin. The reason being that air expands under vacuum. If you have an "overhang" in the object you are casting, the air pocket will expand until it spills out but it will still be full of air! The only way to successfully use vacuum when casting embedded objects is if you pull a full vacuum and then release before the resin sets. If you are using Alumilite, there is just not enough time to do this. Personally, I would not even consider pulling vacuum on PR. I know a lot of folks do to degass the resin but remember, PR is very flammable. I personally do not want to be pulling very flammable fumes out of a vacuum chamber and into the air in my shop!

Pressure works much better. Remember Boyle's Law from your physics classes? (I didn't but have read up on it a lot!). Boyle's Law basically states that for every atmosphere of pressure you apply to a gas, the volume is cut in half. One atmosphere is 14.7 psi so if you cast at 29.4 psi, the bubble in your blank is cut in half. Add another 14.7 psi and it is cut in half again. Cast at 80 psi like I do and you have 5.44 atmospheres of pressure. The bubbles basically go away and are not visible to the naked eye.

Doing vacuum and then pressure does not do enough to be worth the added step in my experience.


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## TurnTex

healeydays said:


> That video shows some of the properties of Alumilite that show it's durability. I like that, but he never mentions the brand of the other but I can't blame him as it would be issues for him with that manufacturer.



The other was a Silmar 41 blank.


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## TurnTex

The other nice thing about Alumilite not mentioned in the quote from me above, is that is sets up real quick. That can be intimidating to folks when they first start but don't worry about having enough time. You will have more than enough. The nice part of it is that you can pour and then put under pressure and remove it from the pressure pot in about 20 minutes. Let it cool down and you can be turning it an hour from when you cast it.

BTW, if you are interested in using Alumilite, I highly recommend Alumilite Clear, not the Water Clear. Water Clear was the original clear formula while Clear is a formula that was developed specifically for turning. It came about based on my feedback to Mike, the Owner of Alumilite. I did all of the testing on it for them and it is superior because it polishes up much better than Water Clear and has a longer open time of 7 minutes vs 5.


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## healeydays

Hi Curtis,

Thanks for joining the conversation. I knew you had a wealth of knowledge from many years working with this stuff. 

Another question was around the dyes. I understand that Alumilite & Pearlex make great pigments, but know there are alot of other specialty dyes out there. What type am I looking for that are compatible with the makeup of Alumilite and Cactus Juice?

Mike B


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## TurnTex

For Alumilite dyes, it absolutely must be free of any water. Alumlite does not like water at all. I recommend staying with Alumilite dyes as they are polyol based which is what part A of the Alumilite is. Some folks use oil based artist paints or even oil based paint from lowes. Personally, I just stick with the Alumilite dyes for all the casting I do. I can get any color I want simply by doing some mixing and really don't feel like messing up resin. Been there, done that!

For Cactus Juice, the water is not so much of an issue. I have experimented with many different types of dyes and found that the Alumilite dyes give the most consistent results. I have had some success with Transtint dyes as well as some powdered aniline dyes.


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## duncsuss

TurnTex said:


> Boyle's Law basically states that for every atmosphere of pressure you apply to a gas, the volume is cut in half.



I agree with the rest of your post, but think this statement is incorrect.

Boyle's Law states that the volume is proportional to the pressure: doubling the pressure from 1 atm to 2 atm does indeed halve the volume, but adding another atmosphere (raising the pressure to 3 atm) doesn't halve it again -- it compresses the volume to 1/3 of the original. You have to double the pressure from 2 atm to 4 atm to halve the volume a second time.

(Boyle also stated this only holds true if the temperature is held constant; Charles's Law describes what happens when the temperature varies.)


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## BangleGuy

TurnTex said:


> For Alumilite dyes, it absolutely must be free of any water. Alumlite does not like water at all. I recommend staying with Alumilite dyes as they are polyol based which is what part A of the Alumilite is. Some folks use oil based artist paints or even oil based paint from lowes. Personally, I just stick with the Alumilite dyes for all the casting I do. I can get any color I want simply by doing some mixing and really don't feel like messing up resin. Been there, done that!
> 
> For Cactus Juice, the water is not so much of an issue. I have experimented with many different types of dyes and found that the Alumilite dyes give the most consistent results. I have had some success with Transtint dyes as well as some powdered aniline dyes.



Just curious, where is the best place to buy the clear Alumilite?


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## TurnTex

BangleGuy said:


> TurnTex said:
> 
> 
> 
> For Alumilite dyes, it absolutely must be free of any water. Alumlite does not like water at all. I recommend staying with Alumilite dyes as they are polyol based which is what part A of the Alumilite is. Some folks use oil based artist paints or even oil based paint from lowes. Personally, I just stick with the Alumilite dyes for all the casting I do. I can get any color I want simply by doing some mixing and really don't feel like messing up resin. Been there, done that!
> 
> For Cactus Juice, the water is not so much of an issue. I have experimented with many different types of dyes and found that the Alumilite dyes give the most consistent results. I have had some success with Transtint dyes as well as some powdered aniline dyes.
> 
> 
> 
> 
> Just curious, where is the best place to buy the clear Alumilite?
Click to expand...


Alumilite.com is the best price.


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## TurnTex

duncsuss said:


> TurnTex said:
> 
> 
> 
> Boyle's Law basically states that for every atmosphere of pressure you apply to a gas, the volume is cut in half.
> 
> 
> 
> 
> I agree with the rest of your post, but think this statement is incorrect.
> 
> Boyle's Law states that the volume is proportional to the pressure: doubling the pressure from 1 atm to 2 atm does indeed halve the volume, but adding another atmosphere (raising the pressure to 3 atm) doesn't halve it again -- it compresses the volume to 1/3 of the original. You have to double the pressure from 2 atm to 4 atm to halve the volume a second time.
> 
> (Boyle also stated this only holds true if the temperature is held constant; Charles's Law describes what happens when the temperature varies.)
Click to expand...


You are absolutely correct sir! Thank you for the clarification. I had been reading it wrong all along! I was aware of the temperature portion.


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