Identifying Acrylic

[James Aldrich]

Hi all,
I was wondering if there is a way to identify acrylic (cast or extruded) if it does not clearly state it on the paper or plastic masking. Most of the acrylic I see in hardware stores just say acrylic or plexiglass. Some have a blue plastic covering, and others have a paper covering. I have etched and cut out a 16x20 photograph on some .236" acrylic found at a hardware store. It came out great. The etching was a little on the lite side.
Thank you.

[Lee DeRaud]

I'm told the easiest way is to engrave and cut a sample:
if the engraved area looks "etched", it's (probably) cast;
if the cut edges look polished, it's (probably) extruded.

[James Aldrich]

Thanks for the reply.
The 16x20 photograph I did, etched well. The etching did not come out a bright white. It was a little softer. I also cut it to size, and it is real smooth and shiny.

Jim

[Lee DeRaud]

Sounds like extruded...most of the stuff you see at HD or the hardware store is.

[Joe Pelonio]

Jim,

Most of the time the blue plastic covered are extruded, the paper cast. It does depend on the manufacturer though, so it's not 100%. Extruded cuts better but doesn't engrave as well, sort of a mushy look to it, less like etched glass.

[Rodne Gold]

Its easy to identify , burn a little piece/strip. Extruded burns silently and drips molten flaming balls , cast burns with a crackly flame and wont drip burning pieces.

[Michael Wells]

That's a great idea Rodne, the only problem is that if you are standing in the hardware store burning their plastic and dripping flaming balls of molten acrylic on their carpet.... Hehehee

I wonder, doesn't the store have to maintain an MSDS sheet (at least in the US) on all of the materials? Maybe that would state the composition. Worth a try to ask them. I suppose if you get one of those young dazed looking clerks, you might have to spell MSDA for them though!
Michael

[Lee DeRaud]

I wonder, doesn't the store have to maintain an MSDS sheet (at least in the US) on all of the materials?I wish! It has to be available from the manufacturer, but I'm not even sure that applies to stuff that's intended for retail sale and is not toxic in its intended application.

That "intended application" business is a real hassle. It's nearly impossible to get some manufacturers to tell you whether something contains PVC or not: "cutting with a laser" isn't an intended application for most retail products.

[Rodne Gold]

Cast acrylic has a minimum +-10% tolerance in thickness and the cheaper varieties can end up at + and minus 20% sheet tolerance. Extruded is alike 1% or so tolerance. If you measure a cut sheet at all edges and its exactly or near to spec , it's most likely extruded. Extruded is always cheaper then Cast. At any rate , even small places will have a plastics supplier or a sign supplier who will definately know the diff between the 2 and will also carry many other lines you can use , worthwhile finding one near you and getting your stuff there. Stuff like polyester vinyl used to laser masks , engraving lams , fixtures and fittings and so on will enable you to come up with different ideas and products.