Need Help Acrylic - Flame Polished - Craze

[Stella_FB700]

Has anybody ever had crazing after flame polishing acrylic (using M. Hydrate/Iso) ?

 

[Sign Works]

Has anybody ever had crazing after flame polishing acrylic (using M. Hydrate/Iso) ?

Yes, flame polishing can cause tiny pours and if alcohol gets in there it expands resulting in crazing (cracks) in the acrylic.

 

[Johnny Best]

I have been poiishing acrylic edges for years with sanding and then compound stick with buffer.
I tried the flame but always had the crazing or something else happened. Even tried the different gases but never got a great result.

 

[MikePro]

I'm no scientist, but I did stay at a Holiday Inn Express last night. YouTube rabbit-hole has plenty of videos regarding this, and attached comments are sometimes useful in explaining what's going on:

Flame polishing basically melting the surface of the plastic. When flame is removed it rapidly cools, causing tensions between surface and core of the plastic. Alcohol naturally disrupts the integrity of the polymer chains and, paired with the tension-issue, starts a chain reaction of micro-cracking, which sucks up alcohol, and causes more cracking.

The cure for this is a process called annealing, in which you heat the plastic up to just below melting-point, and gradually reduce temperature back to room temp.

 

[Stella_FB700]

Thank you guys.

We have just attempted to start flame polishing in house here and we've been struggling.
All responses are appreciated.
Im sure if we can get our clients on a Novus Polished Buff - they should be just as happy.

 

[studio 440]

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[Starter]

As Sign Works posted. Do not use any alcohol ...it will crack the Acrylic. I never clean my edges with anything but a dry rag. Try a sacrificial test piece to get your proper distance and heat. It is not a hard process...just takes a little practice.

 

[Bill Modzel]

I once screen printed a dozen or so pieces of 1/2" thick acrylic that were made to be part of an underwater camera case. I used standard enamel screen ink. No hot thinners or anything and in no place was the ink closer to the flame treated edge than 3/4" . Every one of them ended up with cracks up to 1" from the edge. It really sucked and was quite a surprise as we had printed enamel on acrylic many times, just not with flame treated edges.

 

[vincesigns]

Isopropyl Alcohol and flame treated and/or laser cut edges need to be kept far apart from each other. MikePro has provided the true explanation of why this occurs. I have found that dry microfiber towels are the very best for cleaning and removing fingerprints.