Heat Treat Temperature setting?

[PurpleRobot]

I need to calibrate the temperature setting to heat treat glass lenses on an older air heat treat temper unit. What are the standard recommended temperature points and tolerances for clear glass and/or photochromatic lenses?

We have info with guidelines for tempering duration related to average thickness but not the temperature point. Thanks for any help you can offer.

[FVCCHRIS]

A strawberry pop-tart should completely burst into flames after being introduced after 6.5 seconds! :hammer: Really now, I don't have an answer for you. We quit using Air/Heat tempering long ago. Too problematic and too much of a liability issue. Chris..

[Fezz]

We used to use a strip of some kind of metal, maybe magnesium, insert into oven, and when the temperature was correct...the strip would burst into flames within an allotted time. I will try to dig up my old booklets and see what they say. 1450 degrees sticks out, but I am unsure and need to verify.

[PurpleRobot]

Interesting, my selective memory reminds me of something around 1100 fahrenheit. To further confuse things - one of my lens suppliers is saying 850, which just doesn’t seem right.

Thanks for the research effort; I look forward to what you come up with.

[chip anderson]

Anyone know someone to ask at Corning or Pittsburg? Somewhere at home I have an old book that gives the refractive index of everything (even stuff I thought was opaque, like gold). I am sure that they will have such trivia as glass tempering of thousands of glass compounds and thicknesses.

Chip

[Dave Nelson]

My B&L heat hardex unit calls for 1150F, and I think most should be around the same. Make sure you check your strain patterns on a few culls to insure a good temper.

[Framebender]

Our Kirk is also set at 1150 degrees and works just fine.

Good luck!!

[HarryChiling]

The correct temperature is 1330.

[rbaker]

Heat treating is a function of material, temperature, time and quenching. Each different heat treat manufacturer used different parameters. For a given heat treat unit you must use the appropriate temperature and chart to compute the proper time.

[HarryChiling]

I could scan and send you the information you want post you e-mail or PM me. I agree rbaker that every manufacturer will have different operating temperatures and settings, but if you have a chart with temperature and times it will work on any oven.

[rbaker]

As long as each lens passes the drop ball test . . .

[HarryChiling]

When held under a polariscope the lens should show a maltese cross in the center of the lens, if it doesn't allow the lens to cool and heat again. If done correctly it should pass a drop ball test.

[PurpleRobot]

I need to calibrate the temperature setting to heat treat glass lenses on an older air heat treat temper unit. What are the standard recommended temperature points and tolerances for clear glass and/or photochromatic lenses?

We have info with guidelines for tempering duration related to average thickness but not the temperature point. Thanks for any help you can offer.

I neglected to mention that this is specifically for an old (but sturdy) AIT 407. I sent an email off to AIT about a week ago, so hopefully we can officially close the debate with their reply.

We too used to work with a B&L which had a working temp point of 1150. It will be interesting see if this is ends up being the same for the AIT.

[HarryChiling]

If you have the same chart as the B & L you could use that temp. and chart.

[Dave Nelson]

The heck with salt pan cooking, (see just conversation) I'm gonna start using my hardex unit to save time.:bbg: Toasted marshmallow anyone?

[Framebender]

Am I the only one having a hard time seeing what PurpleRobot is writing or is it time for a new Rx?!?

[foureyes]

i can't read it, it is in white type.
:-)

[Jacqui]

Can't read it here either.

[PurpleRobot]

Am I the only one having a hard time seeing what PurpleRobot is writing or is it time for a new Rx?!?

Sorry about that everybody. I'd changed my default Optiboard colors scheme to the "Optiboard Red" via the forum user control panel. With the red color scheme all text is in white. Looks great to me but I guess it's not too friendly with the default color selection.

Should be back in black now.

[PurpleRobot]

Well it's official.

Direct from AIT, the correct setting to heat treat clear and PGX glass in the AIT 407 is...

1175 Fahrenheit


NOTE: This would be the correct internal temperature that is needed. Some calibration may be required.

[DragonLensmanWV]

The heck with salt pan cooking, (see just conversation) I'm gonna start using my hardex unit to save time.:bbg: Toasted marshmallow anyone?

And it only takes three seconds!
I had a temp worker one time put two CR-39 lenses in the heat treater.Poof!
I also had one put in a PGX lens for 15 minutes, not 5, now I have a very melty looking lens.
And I have a cool set of Grey3 round seg lenses someone put in the PGX chem unit. You can break them with your hand and the outer layer is white, like bone china, whilst the inner portion is grey 3.

[Chris Ryser]

We too used to work with a B&L which had a working temp point of 1150. It will be interesting see if this is ends up being the same for the AIT.

Herat treating has nothing to do with who made the oven any oven that will go up to 1250 F will do.

Heat lens to 1150F and some high minus lenses a little more. Watch out for photograys and browns as they start melting away if left too long.

[Aarlan]

We always used 1200 F in our units

AA