Casting guidance

[BradG]

Hi Chaps
I want to cast some clear acrylic with a black painted tube in the middle. the OD of the blank will be 25mm

I've found this stuff on eBay which looks good for the job
Jesmonite AC100 Non Toxic Water Based Acrylic System For Casting & Laminating | eBay

Though I was curious if anyone would like to give me some pointers on the best methods of approach for mold construction, and anything else I need to know to avoid the common pitfalls like bubbles etc. I am presuming I would be best degassing it before pouring?

 

[theidlemind]

Brad, first pitfall I see I that the eBay product you have picked the resin cures white, not clear.
The pen making standard resins are silmar41 for clear, tube in castings and alumilite for colored blank casting.
Casting Craft makes a clear resing for casting that you can find at a local hobby store.
Check the casting forum for some great mold ideas.
I use PTownSubbie molds and molds made from electric conduit (non-metal).

Steep learning curve but I'm sure you will create something amazing.

 

[skiprat]

Brad, ABL Stevens has just about everything you will need for casting.

I'm sure someone of your calibre can rig up a vertical tube mold with your painted tube down the middle.

A tube mold on a decent sized base can be left on a work bench with any power tool running, on it and the vibration will get rid of the bubbles.

I can lend you a pressure pot if you need though. Axminster sell the pots for not a bad price though.

Have fun!!:biggrin:

 

[Justturnin]

Well you seem to be covered on where to begin. Like the Idlemind stated, this one is white so if your goal is a painted tube it will not work and if you want to color it you will be fighting the white. You need to find something that will cure clear and stay clear. Some Fiberglass Resins are an amber color or will amber over time. Polyester Resin, like stated above seems to be the standard for clear but I know folks in Australia are using Epoxy. I am not sure what limitations you have in the UK as far as products you can purchase.

Also, I have only failed at this, painting Tubes don't use spray paint or any other oil based paint to paint you tubes for that mater. The PR acts as a solvent and will eat the paint up. Water based paints seem to be what you need but I have not done it since my failures but I think folks use enamel paint from craft stores, just be sure to let it cure for a couple of days to get all the water out, or you could just do your fancy chemical treatments on the tube to color it.

Can't wait to see what we are in store for. Watch out you clear casters Brad is about to raise the bar a notch or ten.

 

[Justturnin]

I also wanted to add, when you cast the tube I would recommend packing the tube with something like plumbers putty or palydo. That way if your plug forms a leak there is nowhere for the resin to flow into. I think Dan Ward "Its Virgil" posting something in the library on casting his snake skins and shows how he plugs the brass w/ wood plugs which als act as a spacer to keep the brass off the bottom of the bowl.

 

[BradG]

Brad, first pitfall I see I that the eBay product you have picked the resin cures white, not clear.
The pen making standard resins are silmar41 for clear, tube in castings and alumilite for colored blank casting.
Casting Craft makes a clear resing for casting that you can find at a local hobby store.
Check the casting forum for some great mold ideas.
I use PTownSubbie molds and molds made from electric conduit (non-metal).

Steep learning curve but I'm sure you will create something amazing.

cant believe I didn't spot the white cure lol.. that would have been a palm face moment.... thanks for pointing it out. Silmar 41 is a polyester resin which I cant use. This is why I've selected a casting acrylic. I appreciate its a little unorthodox, but I have my reasons for needing to use acrylic

Brad, ABL Stevens has just about everything you will need for casting.

I'm sure someone of your calibre can rig up a vertical tube mold with your painted tube down the middle.

A tube mold on a decent sized base can be left on a work bench with any power tool running, on it and the vibration will get rid of the bubbles.

I can lend you a pressure pot if you need though. Axminster sell the pots for not a bad price though.

Have fun!!:biggrin:

That's worth considering buying a pressure pot. I keep just touring the idea of buying some 25mm dia acrylic.... but cleaning up the drilled hole so its a seamless transition with the black tube I can see to be problematic. I wonder if simply spray painting the drilled hole would hide all traces of a rough drilled hole, I guess it would stop light reflection so if sanded to 400 etc I think it should hide it well

Well you seem to be covered on where to begin. Like the Idlemind stated, this one is white so if your goal is a painted tube it will not work and if you want to color it you will be fighting the white. You need to find something that will cure clear and stay clear. Some Fiberglass Resins are an amber color or will amber over time. Polyester Resin, like stated above seems to be the standard for clear but I know folks in Australia are using Epoxy. I am not sure what limitations you have in the UK as far as products you can purchase.

Also, I have only failed at this, painting Tubes don't use spray paint or any other oil based paint to paint you tubes for that mater. The PR acts as a solvent and will eat the paint up. Water based paints seem to be what you need but I have not done it since my failures but I think folks use enamel paint from craft stores, just be sure to let it cure for a couple of days to get all the water out, or you could just do your fancy chemical treatments on the tube to color it.

Can't wait to see what we are in store for. Watch out you clear casters Brad is about to raise the bar a notch or ten.

Thanks for the tip on the paint type, il choose carefully

 

[Ed McDonnell]

If you need acrylic for your application, then buying cast rod will probably be your best choice for your applications (whatever that may be).

Sanding to 400 won't be enough. Black paint behind a sanded surface will look frosty, snowy or dandruffy. Here's a link to a video that was posted on IAP a while back on flame polishing acrylic.

How to flame polish an acrylic duck call barrel - YouTube

If you want to try clear epoxy then you could try Epoxacast 690 from Smooth-On. Max cast thickness is 2" (50mm). It will yellow with UV exposure or heat (+115F /+46C). Thick casts can take a loooooong time to cure.

EpoxAcast® 690 Clear Casting Epoxy Resin Product Information

Your best bet here would be to mold the interior as well as the exterior giving you an interior that would not need machining, if your application would allow. If you use Acetal to make your molds you can polish them and get a very good finish on the cast epoxy part.

I always degas resin with vacuum when possible.

Good luck.

Ed

 

[FlowolF]

Brad, ABL Stevens has just about everything you will need for casting.

I'm sure someone of your calibre can rig up a vertical tube mold with your painted tube down the middle.

A tube mold on a decent sized base can be left on a work bench with any power tool running, on it and the vibration will get rid of the bubbles.

I can lend you a pressure pot if you need though. Axminster sell the pots for not a bad price though.

Have fun!!:biggrin:

2nded for ABL Stevens - I get my clear epoxy and clear PU from there and they're both great products (I use very slow curing resins for what I do but their range of products is quite wide and varied), and Jeff (IIR his name right LOL!) is very helpful with any tech or problem solving queries.


FlowolF