building a Polariscope

[BongMcPuffin]

Does this only work only on clear glass? Or can I use it on a heavily colored and worked tube sculpture that you can't see through using normal light?

[catman72]

@BongMcPuffin  alas - only clear glass :-(

[folkertdekens]

sweet and simple thing for quick inspection of my processed polycarbonate pieces, I will make item this week thanks for sharing (catpeople are nice people I dare say) good luck with your inventions, folkert.

[Tamooj]

This is a great DIY polariscope, but I just use my iphone (or laptop monitor) with a white image and a pair of ordinary polarized sunglasses. You can clearly see the stress lines in this manner, and it's very portable. For dark or colored glass you can use a higher intensity light source - I put a camera filter (polarizer) over a high intensity mag-light style flashlight. If the glass is completely opaque (not just darker or colored) this obviously won't work.

[catman72]

@Tamooj - i used to do it with my old Treo , but my current Motorola Milestone

has a different kind of screen. Apparently many new screens have non-linear polarizers,

or maybe no polarizers at all. so i had a few embarracing moments trying to show

the effect in several places, with some screens that simply did not cooperate...

doing it with a small screen and polarized glasses is great when you're out shopping

for glass items, and want to know how well they were made. :-)

[catman72]

@Tamooj (cont.) using a pair of polarized glasses will force you to tilt your head sideways

because the angle of the screen polarizer is about 45 degrees, and you need to be at 90 degrees to it,

so you do it with your neck, or hold the glasses in your hand for it.

i find both ways not comfortable. i prefer holding the glass with both hands, and concentrate

looking at it.

[rocboy2006]

hi catman, I have built a polariscope like the one in your video to check on some glass bongs from my supplier. It's kind hard to tell the stress by this polariscope as many of them are dark colored. I wonder if there is any other way to tell how well the products were annealed or if they were annealed at all.

[catman72]

@rocboy2006

Hi there.

I'm no big authority on the subject (if i were - i didn't have the DIY version...)

but as far as i know - polariscopes are for clear glass only.

if i had a dark object that i needed to anneal, i'd create a thick

clear piece of glass, as thick as the thickest part in my object,

then stress it on perpouse, and anneal it alongside the dark object,

and then check it on the polariscope.

i suspect artists incorporate a clear part in their art

just for this purpose.

[rocboy2006]

@catman72 Thanks for your advice. Some of glass bongs I received do have a clear section, but that section does not seem to be stressed hard as other parts, so I can't really tell the stress for colored by checking only on the clear section.

They are made of borosilicate glass, size is about 4mm thickness, 500mm in length. Is there other way to check if they are annealed?

[catman72]

@rocboy2006

as far as i know- no way to check dark coloured glass.

how can you tell that "...that section does not seem to be stressed hard as other parts"?

if you anneal according to the right tables for your type of glass (time as function of thickness)

you should be OK, unless you have comaptibility issues between your

glass colours, because of different manufacturers.

did you have any breakage ?

[rocboy2006]

@catman72

Sorry I have to write a separate reply due to youtube's word limit. By the way, I did a temperature shock experiment in which I freeze the bongs in my household freezer around -10C for 30 mins before taking them out and letting them warm up in room temperature about 20C. They didn't break. I am not sure if that is sufficient to conclude that they were annealed.

[catman72]

@rocboy2006

seems perfectly good.

i can only suggest re-checking annealling tables for your specific glass,

and perhaps a longer soaking time and longer ramp-down?

make test pieces of any colour you have + your clear base-glass, and

anneal and check in a polariscope for any incomaptibilities.

that's all i can say.

ask Acroduster if he has any good idea.

[guitargraham1]

Thank you so much catman. ! this is the best thing i have seen on you tube in a long time. :)

[catman72]

@guitargraham1 - Thanks man, thats the best comment i've got on YouTube

in a long time :-)

[pidner]

I would like to make one of these for checking inclusions in gemstones,I was wondering if the camera lens filters I saw at walmart for $20.00 are the same thing as I am building mine smaller about 2" in diam.and about 6" high.I seen a website on google showing how to make them,but it didnt show where to put the stone to examine it,I assume on a table under the bottom filter?

[catman72]

@pidner - for gemstones there are 2 filters that are used,

one is linear (the kind used in this video) and the other is circular (as in some camera lenses)

depending on what phenomena you want to check in your gems.

for the linear filter you can use many old LCD screens, from calculators to

old Palm devices. camer filters also, but check to see what type.

old (or cheap) polaroid glasses too.

the circular filter your are most likely to get in camera lenses.

[pidner]

@catman72 I dont know what made me say inclusions,I use it to check the reflectivity of the stone ,and I did use a old but good set of polarized sunglasses to make my polariscope,also I bought a 58mm polarizer filter and use it with my computer screen,in word pad mode if the stone is to small for my homemade polariscope,and thank you for your reply,your information is right on the money.

[catman72]

@pidner i will soon build a small portable polariscope that might help

people who buy gems, though it's ment to help those buying glass objects.

something in the spirit of "project in an Altoid box" like in Instructables .

it's for telling if the artist truely anealed the piece you are about to buy.

intended to be pocket sized. when it's ready i'll make a video.

[pidner]

@catman72 Great,Id be very interested in seeing it,I also go over to Instructables and give it a look every now and then,theres some very helpful and fun projects on that site,I built a smoker for my brother out of a large clay flowerpot buy following one ,I go by the name spylock over there.

[duanedaniell]

I love it! Recycling technology for applications never intended. You Sir, do indeed Rock!

[acroduster]

you sir, Rock!-)

I am so building one of these!-)

I have a couple of old laptops and screens laying around, now I know what to do with them.-)

[catman72]

hey now, you're supposed to work on

the more important stuff !

don't waste your time on this,

let the kid build it :-)

[TimiaGlass]

Very cool idea. I would not of thought of using the LCD screen for the back side.

[catman72]

been playing with LCDs and polarizer filters for 2 months before it hit me :-)

now my optician uses my setup to see

if incoming lenses are tempered.