New to casting, what size to make molds?

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BillS

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Nov 13, 2008
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Northfield, MN
I am just starting to get into casting alumilite with and HF pressure pot. My plan is to use 1/2" "plastic" to create molds. Would anyone have any recommendations on what size to make the interior cavity for the most versatility?
I am also returning to pen making after about a 15 year absence and am amazed at the number of different pen tubes/types available. Is there a recommended mold length to allow for efficient use of material for both single tube and double tube pen types?
Lastly, is there a recommended size for casting bottle stoppers?
Thank you for any insight anyone is willing to provide.
Bill
 
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RetiredGuy23

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If you are just getting started casting your own pen blanks, I believe you should start with Silmar 41 instead of Alumilite. It is much cheaper. 3/4"x 6" pvc pipe makes a good starter mold.
 
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If you are just getting started casting your own pen blanks, I believe you should start with Silmar 41 instead of Alumilite. It is much cheaper. 3/4"x 6" pvc pipe makes a good starter mold.
I agree 100%. I bought one long piece of 1" OD pvc pipe and cut it up into a boatload of molds. You're going to have a learning curve, best to practice with the cheaper stuff. Another plus for Silmar 41 is that it polishes to a higher shine than Alumilite, at least IME.
 

endacoz

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if you have a shop you heat in the winter or can't ventilate well GO with alumilite. Not that big a learning curve. more tools needed. I heat my detached garage and there is no way I could cast PR or other resins that have a toxic smell in my shop and stay in there.

Any alumilite questions feel free to let me know. I've already sold over 200 alumilite hybrids this month.
 

BillS

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Northfield, MN
Thanks for your advise with the Alumilite. Like you, I live in Minnesota and a heated shop is a must. After attending a seminar recently I have decided to go the Alumilite route. Can you provide any advice regarding mold sizes to cast blanks? I am planning to use HDPE to construct the molds but am not sure what size to make for efficient use of the resin. In addition I would like the mold size to allow to cast different pen blanks from the same mold.
Thanks for your help.
 

Skie_M

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Bill ... the typical size for pen blanks sold and available commercially is around 3/4" round or square by 5" - 6" long


You could get away with 5/8" round, and some people prefer having 1" round. Round is pretty simple to do if you use PVC pipe for your molds, and a simple cork with a plastic baggie over it to stopper the end. Make the pipe around 6 - 7 inches long so that you aren't in danger of spilling overage, and after it's cured it will simply pop loose without the use of a mold release agent. (Alumalite shrinks a tiny bit when cured.)

To make the large swirled patterns you see available through PSI and other places, they typically use some metallic flake imbued or pearlized dyes and a large squared or rectangular pan made of HDPE cutting board or other similar material. I've seen some suitable material available from Academy Sports in their outdoor cooking area - a very large cutting board 3/8" thick, perhaps 18" x 24" surface. It was around 25 dollars, but I think one of those would suit for making several rectangular blank molds.

Once you've got the mold built (use screws so you can knock down a side to remove the alumalite easily), you just need to add some silicone to the inside corners to ensure that it will be leak-free. Mix your alumalites and dyes, pour them in carefully after allowing them time to "pre-set" so that they won't easily flow into each other and mix the colors ... and gently swirl them together to create your desired patterns.

The mold dimensions can be pretty much whatever YOU want for your own convenience .... the finished alumalite block can be milled down into pen blanks with a table saw or band saw. You want at least one dimension to be 5 - 6 inches, with whatever dimension you wish for the other direction, as long as you get a reasonable number of pen blanks from it.
 
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BillS

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Northfield, MN
Thanks for the information. I've decided to go the plastic mold way. Today I searched around for cutting boards but the only ones I could find where a 1/4" thick...until I went to Costco. Costco has a set of three plastic cutting boards which are all 1/2" thick. The set has one 15"x20" board and two 15"x10" boards. The cost is only $19.99. This should give me plenty of material to get started.

Is there a standard blank size for bottle stoppers?
 
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