Re: [Killietalk] WEld-on??

[Wright Huntley <whuntley at verizon_net>]

>
> In a message dated 4/7/04 1:39:57 PM, cgraseck at optonline_net writes:
>
> << My experience is that one should never use alcohol of any sort on
> acrylic.  >>


Many years ago, I had a project that needed an intricately-machined 
shape, that we made starting with cast (maybe extruded?) acrylic tubing.

Overnight, the beautifully turned 2"X6" piece developed cracks all over it.

The second one did the same.

I figured machining generated incipient, but invisible, cracks and that 
thermal changes overnight forced the cracks to grow. I don't remember if 
we cleaned it with alcohol, but think it was more likely that we just 
used water and a bit of detergent to remove coolant residue.

I saved the third one we made by annealing it in a beaker of water. I 
set an aquarium heater to a very high value (180-190F) and slowly heated 
the piece, allowing it all night to cool in an insulated space.

Never had another crack, after that, and about 8 of them operated in an 
outdoor setting for many years, as I recall.

Acrylic is a very glassy material, and any initial crack takes very 
little external disturbance/force to make it propagate. It's like the 
way a glass cutter starts cracks in glass, and minor external stress 
pops them through the sheet.

I agree with the suggestion to use the Weld-On to seal edges, as that 
should work better than annealing, and beats hell out of uniformly 
heating/cooling larger sheets.

Wright

PS. Denatured alcohol is ethanol rendered tax immune by added "stuff" 
that makes you sick. It is not a good idea around tanks (makes fish 
sick, too). Isopropanol (aka propanol-2) is very different and is the 
main one in rubbing alcohol. Cheaper versions have only isopropanol and 
water. Fancier ones have added lanolin o/e to keep from drying skin. 
Read the label, for you do not need any oils in your fry water.
--
Wright Huntley - Rt. 001 Box K36, Bishop CA 93514 - whuntley at verizon_net
                    760 872-3995

        Eschew obfuscation and bloviation!



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