Alumilite or PR bowl

[Woodchuck]

I know this is a pen turning site but I know most of you also play around with bowls too. I had the idea of making a PR or Alumilite bowl and was curious if anybody on here has had the idea or done it themselves. I want to know how much casting agent to use to make a 8x4 in. bowl. I also would like to know how it turned out and if there was any problems turning it. I talked to one of the guys at the local Woodcraft and the guy mentioned he had the idea but bought a 2nd hand bowling ball, cut it in half and turned 2 bowls out of it. I guess it is similar to PR or Alumilite casting. If anybody had any answers for me or any idea that would help me, please send me a PM.

 

[MesquiteMan]

I have done small bowl blanks but for the bowl size you are talking about, it would get expensive pretty quick. I only use Alumilite so can not speak for PR other than if you do one out of PR, you better treat it like a glass bowl when using it since PR will shatter if you drop it.

As for the amount of resin...if you start out with an 8x8x4" blank, that will require 141 ounces of Alumilite. At roughly $80 per gallon when purchased as a 2 gallon kit, that works out to $.625 per ounce making your blank and $88 bowl blank! Of course you could cast it round already and save some money with the resin needed working out to 11 ounces which is still a $70 blank! If you wanted to figure it for a different size, it takes .554 ounces of mixed Alumilite per cubic inch of finished casting.

 

[PenMan1]

A Shedd Spread Country Crock fake butter package makes a great PR bowl mold. Just measure the bottom of the container to make sure it is wide enough for your needs.

As far as how much PR to use, measure up the side of the container to 5 inches (if your bowl depth is 4 inches, you need a little chucking room). Then fill the container to the mark with water, the pour the water into a large measuring device (Redneck Volume Calculation). That is how much acrylic you need. Just be sure to completely dry the container before pouring PR--PR AND WATER ARE NOT GOOD FRIENDS.

I recommend using a round mould because "the right size" is usually plentiful in the TupperWare bin in the kitchen AND working with a round blank greatly simplifies turning acryic bowls. Most chipouts, dings and gouges come from trying to round a square PR blank.

 

[PenMan1]

IMHO, PR is a far superior choice for bowls than Alumalite. First, Alumalite can never really achieve the gloss that PR gives. Secondly, while "technically" Alumalite is less brittle, PR is much easier to cut without voids and actually has a little more flex in applications this large. Third, PR is considerably less than half the cost of Alumalite and in this type application yields a much more pleasing final result.

 

[ttpenman]

First of all, I'm not a bowl turner. Tried a couple times but never got the hang of it. Having said that, would it be possible to make a wood bowl form (just the inside turned) and another smaller form (just the outside turned) cut so that there was a 1/2" to 3/4" space between them when they were stacked. Then put a piece of wood across the top, screwed into each piece to maintain the distance between the forms where the resin would go. Hope that made sense. The issue is this, can you coat the wood with mold release or maybe stretch clear plastic wrap around the wood so the resin wouldn't stick. Would really cut down on the amount of resin. Fill the mold with water to get the amount of resin.

Will this work?

Jeff in northern Wisconsin

 

[Woodchuck]

Thanks for all your input. I thought it might be kind of expensive, thats why I havent done it yet. I figured PR would be easier to turn. I had some Alumilite laying around that I have had forever and not sure if it has a shelf life or not but I figured I should use it so I got a tupperware bowl and poured it in. Alot of air bubbles but we will see how it "turns" out..lol

Jeff, I thought about doing that too. It would def cut down on the amount of PR used. Will probably give it a try.

 

[Craftdiggity]

You could always make a mold out of urethane rubber or silicone rubber. First turn a bowl out of wood and then use that to cast the mold.

 

[Bellsy]

Have you given any consideration to the thought of turning a worthless wood or mutt bowl with the alumilite? Just a thought.

Dave

 

[Woodchuck]

Chris, I never thought about that but that's one great idea. I could get one for the outside and inside which would save on the amount of casting and time of roughing out the inside. I'm a newbie at casting so where do I get rubber or could I make it myself and where do I get the stuff for it and how would I go about getting it done?

Dave, by worthless wood do you mean like what they do those Fiji blanks you get from Woodcraft? I'm not sure what you mean by mutt bowl. If the worthless wood is what I'm thinking your talking about, that would look awesome to make it look similar to the pen blanks. Don't you need to put it in a pressure pot? I don't have one and dont know anybody around me that does casting so not sure how I would go about that one.

 

[Craftdiggity]

You can get urethane rubber from US Composites, which is where you can also get resin incidentally. This is a relatively inexpensive product, but not as long lasting as silicone rubber, which can be purchased from the good folk at Smooth-on.com. It is much more $$$, but a better product as well.

 

[workinforwood]

Best thing to do is to make a mold and pour your bowl. Making the mold can be just as fun as making the bowl itself. You make an outside and an inside, then you need to jig it up so the inside sits perfectly inside the outside with an even space all around it. I would make the mold out of blocks of Aluminum because they will polish and shine up the best but you could use resin like delrin or plexi blocks and be sure they are well polished. Now you can make a multitude of alumilite bowls at minimum cost. Oh...but there's more to the story! you can now use plain white alumilite, to further reduce cost, and make it even less brittle! you can paint you mold with water based paints..have lots of fun with that..let the paint dry. Now pour in your white alumilite..all the paint you put on the mold will now be on the surface of the alumilite, totally chemically bonded so you need to actually take a knife and cut into the bowl to remove the paint! Also..it will be super shiny! Because you don't need to wet sand and polish the bowls, they will come out of the mold perfectly shiny, as shiny as PR can get. The thing about alumilite, it can shine up as bright as PR, but it's a hundred times the work, because the product is more like super hard rubber than glass, it takes far longer to remove sanding marks and far more grits of paper and lots of rinsing and soapy water really helps. When you pull something out of a smooth mold, there is no sanding, no sanding marks, already perfectly poured smooth and super shiny. It's just like when I make a block of resin. If I set my block of resin next to a block of PR like Johnathan's, you wouldn't know the difference, the top of each block is going to be so shiny it looks wet. People make replica tail lights, dolls, medical supplies, tons of applications using alumilite and mold technology. The way it reacts to a painted surface makes it a real favorite with toys because there is no worry about paint coming off the surface. Pens barely scratch the surface of what the product is all about.