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Polishing the edges of acrylic

brdesign

brdesign

New Member
A much slower but less risky way is to sand the edges with progressively finer grits of sandpaper. Start with 150-200 and work up to about 600-800; for an extra fine finish, use some polishing compound. With flame polishing you want a pretty smooth edge to start with so have a rough cut edge us some sandpaper to knock it down and then flame polish.
 
Stacey K

Stacey K

I like making signs
brdesign said:
A much slower but less risky way is to sand the edges with progressively finer grits of sandpaper. Start with 150-200 and work up to about 600-800; for an extra fine finish, use some polishing compound. With flame polishing you want a pretty smooth edge to start with so have a rough cut edge us some sandpaper to knock it down and then flame polish.
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I don't have a torch so I think this is the way to go. Thanks!
 
Gino

Gino

Premium Subscriber
Go to harbor freight and get a cheap torch and 2 cylinders and practice. Just get one with an on/off switch on it, so there's no risks. You'll be surprised all the things the torch will come in handy for. Getting ahard to get at areas to weed whack, killing grass in cracks, post-heating wraps, polishing plastics and you can even cook with it.
 
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rossmosh

New Member
Sanding is definitely the safest and most repeatable method. I gave up flame polishing after talking to an acrylic specialist. He basically repeated all the issues I had with flame polishing and told me he'd never flame polish. He had a super expensive diamond polisher but he always recommended just sanding and if necessary, buffing. Personally I find sanding to 500/600 grit to be more than acceptable.

You do want to take your time sanding at the 150-180-220 grit period. You really want to get as consistent of a finish as possible at that point. That way when you jump to 500/600 grit, it's just polishing. More than once I thought I was done only to have to go back to a lower grit to sand out a bit of a saw/router mark.
 
Scotchbrite

Scotchbrite

No comment
Make sure you use the correct gas in the torch. We used the wrong gas and got a bunch of crazing. I was a long time ago and I don't remember which gas and which plastic we were using. Our plastic supplier was able to set us straight.
 
Johnny Best

Johnny Best

Active Member
Buffing wheel on an electric motor with compound brick.
Just polished some edges today. Hard to take a good pick with IPhone.
 

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Superior_Adam

New Member
The proper way we were told to do it is a torch with a mix of oxygen and hydrogen. We take the pieces off our router and can polish the edges of a 4x6 sign in about 5 minutes. Other gases will work but the edges might not be as clear. It was explained to us that hydrogen is a “cleaner” gas and the temp with the hydrogen/oxygen is ideal for getting a crystal clear edge.
 
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ikarasu

Active Member
Careful with a torch these days.

Everyone is using 70/30 alcohol mix due to covid - we've done flame polished for years with no problems... All of a sudden the last 2 years the crazing has been really crazy, janitors have a bottle of 70/30 and tend to use it on everything.

The below video is an extreme case... But we've had dozens up acyrlic panels that have been up for years with no issues all of a sudden start getting cracks when covid happened.

Most of ours are in schools and hospitals where alcohol is very prelevant... So maybe we just have bad luck.


 
GAC05

GAC05

Quit buggin' me
ikarasu said:
Careful with a torch these days.

Everyone is using 70/30 alcohol mix due to covid - we've done flame polished for years with no problems... All of a sudden the last 2 years the crazing has been really crazy, janitors have a bottle of 70/30 and tend to use it on everything.

The below video is an extreme case... But we've had dozens up acyrlic panels that have been up for years with no issues all of a sudden start getting cracks when covid happened.

Most of ours are in schools and hospitals where alcohol is very prelevant... So maybe we just have bad luck.


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Wonder if he forgot and washed his left hand with alcohol after burning it?
 
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netsol

Active Member
we use something like this

 
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letterworks

Premium Subscriber
The easiest way for a small shop to flame polish is the little "brown's gas" machines that you probably can pick up on amazon or ebay for $200-300. It uses chemistry to make the hydrogen (and some of the oxygen) and has a small torch too. Way cheaper than the "real" setup with the bonus of portability.

When polishing acrylic, we consider it a must-do to inform customers of the positives and negatives. Positive is the (relatively) quick shiny edge and no sharp corners. Negative is the chemical resistance, particularly to isopropyl alcohol but also Windex and other common cleaners. We try to have a disclaimer go out on all our polished pieces.

However, in practice, all these problems are less with Cast acrylic too (laser cutting polished edge is also less problematic), so you could only use cast for jobs that you polish.
 
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letterworks

Premium Subscriber
Yah we bought one. It works fine but we haven't used very much as we have the real setup. The flame is relatively small but that's sometimes a good thing but it does end up slower too.
The chemical mix goes brown after a while so maintenance is a little unknown (still worked the last time we used it though) and of course it's Chinese and the manual is crap but maybe someone reselling has made a better manual.
 
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