Why did my alumilite cast pinecone crack?

[kuraki]

This is my first attempt at pressure casting. I thought I followed all the instructions and various videos to a "t." But when I started sanding my block down (this was to be for a hidden tang butchers knife) I noticed these cracks. Almost all of them are adjacent to a pine cone petal. I threw a quick buff on the rough sanded block to check my color.

-Cast with alumilite clear, mixed by weight (104 grams of each A and B for this pour)
-Mixed with alumilite blue dye and pearl metallic powder, into side A before combining
-Combined A and B and mixed very well, for 3 minutes
- At 5 minutes I had it in the pressure pot and it was pressurized at 50 psi
-Left under pressure for 1 hour before demolding

Prior to this, I had stabilized the pine cone under vacuum with cactus juice, followed all instructions there as well, under vacuum until bubbles quit, then soaked 2x as long, then baked off at 200F for an hour.

Pretty bummed about this, I really enjoy doing things like this, making micarta, etc, really anything that the majority people say "you're better off just buying it than doing it yourself." Well yeah, then none of us would be knife makers either. But this stuff is too expensive and time consuming to do much trial and error.

 

[Fish30114]

kuraki, I have cast quit a few bits in Alumalite, with good results, and actually only used my pressure pot once though just FYI, the only thing I noticed that you stated that I did differently was that I mixed the two parts (A&B) together first and then I added the pearl/color, I even casted a pine cone also stabilized in cactus juice same as you're saying--I had no cracks in mine though!! I can't see where this would make a difference, but it's the only thing I noticed that was different.

Good luck--Don

 

[kuraki]

Thanks Fish. I do recall reading on a penturning forum that they do the same thing you did, the only reason I did it differently was because of Alumilites youtube videos. I'll try mixing the dye after combining the parts next time.

 

[Tkrocky]

Was your pinecone completely dry and clean? I have cast pinecones and a bunch of stuff in alumilite and the only time I've had problems is when I wasn't able to get the pinecone clean enough


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[mete]

I would have thought it was moisture in the cone.

 

[kuraki]

Tkrocky, how did you clean them? They were dry because I baked them but there was some sap and I'm thinking that was the issue.

 

[Tkrocky]

What type of pinecone was it? It's best to get a hold of a real old one, and makes sure it wasn't scented for some decoration or something. I wash mine in a bucket of dish soap and then dry in the oven like you said


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[kuraki]

I have some huge white pines so it was one I found in my yard. I found some craft people discussing cleaning cones, and I tried their method on my second attempt here. Soaked in white vinegar/water mixture then brushed clean, this got them pretty clean. All the visible sap came off. Then I put it in my food dehydrator overnight at 155F.

Still got some cracks/voids. The voids I'm pretty sure are a result of how much space the cone took up in my mold, but the cracks are what bother me because they seem impossible to fix. I'm kind of at a loss. I'm going to make one more attempt, cleaning and drying the pinecone for a week maybe, something ridiculous, since it seems that this has to be a moisture issue.

On the positive side this is my 2nd attempt at a forged blade (1st cracked in quench) and I'm pretty happy with how it's turned out other than the handle.