Plexi turning White...HElP

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LandfillLumber

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Hello, I'm getting my plexi turning white when I wet sand, I was thing that maybe I'm heating up the plexi running the lathe to fast(maybe). It does not show up until I start sanding. Thanks, Victor
 
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Isn't it supposed to turn white when you sand? Maybe I'm missing something here but ca turns white also. Just keep sanding with finer grits and it turns clear again. I've GOT to be missing something![?][8]
 
Victor - That's the nature of the beast with plastics. When you start sanding, you create scratches that are large but smaller than tool marks. Those scratches show as white, although they are actually opaque. As you progress to finer and finer grits, smaller scratches replace larger scratches and the plexi begins changing to transparent. At the end, a bit of plastic polish will leave a near-glass appearance.
 
When you are sanding are you wet sanding or dry. I have never experienced it turning white after sanding. I have however had it turn white during the application.
 
Not sure what type of plastic, it was just plexi scrap I had forever. Its not the white from sanding, sorry I did not explain very well, It seems to appear out of no where. It has happened when I polished it with Novus as well, this is why I think it is a heat problem. I'm wet sanding these blanks and still I get these white patches showing up, its weird. Thanks everyone, Victor
 
A quick way to tell if it is Acrylic or not is to take a scrap piece and light a match to the edge. If it quickly melts and turns brown/black, it is most likely acrylic.

Lexan will hold up to a higher heat than a single match flame can produce.

Try pausing for a few moments between sandings, leave the lathe running for the air flow. If you have an air compressor hit it with a short blast from an air gun. Acrylics need to run as cool as possible.
 
My plexi sometimes turns white in the cold weather after applying and just spinning to dry. The white part sands off with the 1500 MM. I apply 40 coats of thin plexi just as quickly as I can put a drip on the paper towel and slide it across the blanks - total of 3 minutes, tops.

Do the white patches look like they are in the finish, or below the finish? Wet sanding shouldn't produce much heat... You got me stumped.

Chris
 
If you could give description of your process it would help. Are you wiping the blank down or not. How old is your solution.
 
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