| Van down by the river |
10-05-2003 05:55 PM |
Quote:
because plexi glass will turn yellow and go brittle after awhile.
|
This is incorrect. Acrylic/Plexiglas will not turn yellow and brittle. I have seen plastics change after prolonged exposure to the sun (years). These pieces were not acrylic. They were a very cheap plastic, which would be unsuitable for aquariums anyways.
Occasionally I have seen brittle plexi but it is usually from poor manufacturing. Old Seaclear aquariums used very thin plexi. They flame polished them, after a short time the tanks would show crazing. Crazing looks like crystallization or a dense web of hairline fractures in the acrylic. The tank can often perform well even with crazing although, early seaclears seemed prone to splitting (material was too thin).
Crazing is caused by flame polishing which is the process of a flametorch being brushed past the surface of the acrylic to instantly superheat the acrylic. It softens or liquefies the outermost layer of the acrylic and then when it quickly cools, it is now smoothed. It's the lazy way of buffing the edges. It's fine for food bulk bins but, not for aquariums. Unfortunately many fabricators see an aquarium as just another box. The fast heating and cooling of the outerlayer can cause the small fractures. Sometimes it's not evident at first but with prolonged pressure from the water inside the unsightly fractures develop.
If you are fabricating a tank ask them how they polish. If they say they flame polish, consider finding another builder. Manual buffing will cost more but in the long run is a good investment. Manual buffing requires time as it is physical labour as to Flame polishing which takes seconds.
I know of many tanks that have been around for longer than most hobbyist have been in the hobby, and the tanks still look great. I'm not so sure about the hobbyists though! :eek: |
