Polarity? (translucency in all directios)

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Dan_F

Dan_F

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A question for casters: In store bought acrylic blanks one can typically only see deep into a blank from two directions, let's call them north and south. The east and west views tend to be rather dark, like two polarized lenses turned 91* to each other. Can anyone explain that to me, and do you get the same effect when casting at home, or does it depend on how you layer the resin as you pour?

I could see that effect happening with the layered ribbon sort of method, but wonder why it occurs with the crushed "chip" type blanks as well. I find it annoying, will I be able to get around that if I cast my own?

Thanks,

Dan
 
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Dan, I think what you're talking about is 2 sides shine & look like you can see it differently. While the other 2 are dull from being run thru a saw. Sand & polish one of the dull sides & it should look the same. Or just wet it. All blanks I've used are basically the same all the way thru. Once turned and sanded to 12,000 it always looks the sams all around.
 
There is a "Pink Flamingo" blank that woodcraft has that when you turn it 90deg its no longer pink but lets of a white pearl shimmer. I dont think I have seen any homebrews with this type of polarity...
 
Originally posted by MobilMan

Dan, I think what you're talking about is 2 sides shine & look like you can see it differently. While the other 2 are dull from being run thru a saw. Sand & polish one of the dull sides & it should look the same. Or just wet it. All blanks I've used are basically the same all the way thru. Once turned and sanded to 12,000 it always looks the sams all around.
Click to expand...

It actually looks basically the same whether square or round. It's kind of like a trout, the sides are flashy, but the back and belly are kind of dull. With the blanks, the sides are reflective, while the "back and belly" are not, and get sort of dark. So the pen ends up with two attractive sides and two kind of dark, blah sides.

This is one of those cases where a picture is worth a thousand words.
Here are three blanks, turned round, but only one is finished. The other two are just partially turned with a skew. The first pic shows the good side, the second, the dark side. Note that the blue and green looks good from all sides, the others suffer from the polarizing effect. Same blanks, just rotated one quarter turn. The blue and green one always looked good from all sides, so it's not just that it is turned down to final size and polished. These blanks all came from Woodcraft.

P1020080.jpg



P1020081.jpg


Dan
 
Originally posted by el_d

There is a "Pink Flamingo" blank that woodcraft has that when you turn it 90deg its no longer pink but lets of a white pearl shimmer. I dont think I have seen any homebrews with this type of polarity...
Click to expand...

Some if that is due to the way they layer the pearly stuff (left and center in above pics), but I don't see why it should affect the ones with crushed bits like the one on the right. Even on the swirly ones it's inconsistent, some have dark side, some not.

Dan
 
Originally posted by Dan_F

A question for casters: In store bought acrylic blanks one can typically only see deep into a blank from two directions, let's call them north and south. The east and west views tend to be rather dark, like two polarized lenses turned 91* to each other. Can anyone explain that to me, and do you get the same effect when casting at home, or does it depend on how you layer the resin as you pour?

I could see that effect happening with the layered ribbon sort of method, but wonder why it occurs with the crushed "chip" type blanks as well. I find it annoying, will I be able to get around that if I cast my own?

Thanks,

Dan
Click to expand...

Dan; Yes; This effect results from the casting of acrylics in large sheets which have a "top" and "bottom". When the sheets are cut into pieces you see the "sides" of the material. If you want to avoid this in purchased blanks, look for "rod" pieces. If they are true rods, they are extruded rather than cast and are consistent side to side.

You can avoid this when casting your own.

Hope this helps......
 
Randy---Some of the rods I got in the group buy do the same thing.[V]

Scott---Luckily this is what I would hope to avoid in home brewing.

Dan
 
Dan-- I've bought at least 100 blanks from Woodcraft & have never seen such as that. No good like that. I'd take it back to them & either try another one or get something different. I did the Wallstreet/Abalone & the blank didnt look right & they swapped it out for another. Normally very good people to work with.
 
MobilMan said:
Dan-- I've bought at least 100 blanks from Woodcraft & have never seen such as that. No good like that. I'd take it back to them & either try another one or get something different. I did the Wallstreet/Abalone & the blank didnt look right & they swapped it out for another. Normally very good people to work with.
Click to expand...

I've gotten a lot of blanks from Woodcraft like that. Not all, but definitely some.

BTW my customers tend to like the polarity, gives it another dimension of shimmer.



And as far as some blanks being rods, just know that a LOT of the "round" blanks out there are merely machined round from a square blank. Email Ernie at Beartooth and ask him about his round acrylic rods-- he told me that his supplier paid a subcontractor to machine them round for some reason. I prefer them round since I drill on the lathe, makes centering easier and makes turning them quicker (less chips of acrylic in my hair, mouth, etc...).
 
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