Heating of CR-39 lenses

[chance]

Hey all, I have been researching and experimenting with Carl Zeiss CR-39 lenses. My aim is to make the lenses softer because I am popping them into some brittle frames that have a tendency to crack during lens insertion. I have read that CR-39 is a thermoset plastic that will not soften when heat is applied, but in my experiments I have found that a quick minute in the microwave makes them very bendy. I have also read that others have seen them soften while tinting, and have read rumors of lenses shrinking in places like a hot car in Arizona. My question is this:
Does anyone have experience heating CR-39? Has anyone seen permanent damage? i.e. warping, clouding, brittleness, distortion or otherwise after heating CR-39 lenses? Thanks very much for any input.

[rbaker]

CR-39 is a thermoset plastic that will not soften when heat is applied, but in my experiments I have found that a quick minute in the microwave makes them very bendy.

The molecular structure is altered by heat and is irreversible. Its somewhat akin to changing a pickle back into a cucumber. Not a recommended procedure when a few seconds on the old hand edger will allow you to precisely size the lens. And, if I may be so bold as to ask; why are you glazing old brittle frames?

[PRECISIONLAB]

Great to see someone thinking outside the salt pan .

In my opinion microwaving lenses just sounds bad. When processing any type of lens we are trying to avoid heat whenever possible.

I see why you are trying to soften lens but perhaps soaking in a warm water bath may help. I do this to relax any stress in lens such as blocking disc marks on trans. This may allow for some flex in the lens.

If you are looking for a "pliable" lens perhaps poly or trivex.

Are the frames you refer to old or the new acetate style frames?

[chance]

The molecular structure in altered by heat and is irreversible. Its somewhat akin to changing a pickle back into a cucumber. Not a recommended procedure when a few seconds on the old hand edger will allow you to precisely size the lens. And, if I may be so bold as to ask; why are you glazing old brittle frames?

You certainly may ask. My frames are made from unusual, natural materials which are prone to cracking. I have lens edging capability and don't see breakage that often, it's just expensive when it does happen. I have less problems putting in Polycarbonate lenses which are noticeably more flexible, so that's my aim: to soften the CR-39.

[chance]

Great to see someone thinking outside the salt pan .

In my opinion microwaving lenses just sounds bad. When processing any type of lens we are trying to avoid heat whenever possible.

I see why you are trying to soften lens but perhaps soaking in a warm water bath may help. I do this to relax any stress in lens such as blocking disc marks on trans. This may allow for some flex in the lens.

If you are looking for a "pliable" lens perhaps poly or trivex.

Are the frames you refer to old or the new acetate style frames?

My frames are made out of different species of domestic and tropical hardwoods

[PRECISIONLAB]

I have heard of such frames but have yet to see or work on any. Kudos to you on your custom work

[Chris Ryser]

I have some patents on tinting lenses in a microwave. So I have had the experience with hundreds of them. CR39 is the easiest to do, and they withstand the heat easy. They might go a bit soft while under heat but go back to their original state when cooled off.

Some hard coats used to come off when heated too long, because they are harder than the lens material.

[EyeManFla]

you get a naked cr-39 lens and you can heat and bend the crap out of it....looking through it, on the other hand.....

[Chris Ryser]

you get a naked cr-39 lens and you can heat and bend the crap out of it....looking through it, on the other hand.....

.........are you saying that you produce your own cylindrical lenses by hand ?

[uncut]

Hey all, I have been researching and experimenting with Carl Zeiss CR-39 lenses. My aim is to make the lenses softer because I am popping them into some brittle frames that have a tendency to crack during lens insertion. I have read that CR-39 is a thermoset plastic that will not soften when heat is applied, but in my experiments I have found that a quick minute in the microwave makes them very bendy. I have also read that others have seen them soften while tinting, and have read rumors of lenses shrinking in places like a hot car in Arizona. My question is this:
Does anyone have experience heating CR-39? Has anyone seen permanent damage? i.e. warping, clouding, brittleness, distortion or otherwise after heating CR-39 lenses? Thanks very much for any input.

You will typically cause a Cr39 resin lens to expand(swell) if you heat it...especially during tinting. I would suggest that you edge them to the ultimate shape and size, and cold insert with lubrication, using a material like baby powder. I would also suggest trying to chill the lens instead of heating it, especially if it was tinted earlier in the day of edging. Just an opinion, with practical experience.

[CME4SPECS]

by heating a lens and inserting it into a frame, you no doubt will change the intended curvature of the lens, which will alter the rx...not a good idea.
I have heated warped lenses to get them soft enough to flatten them a little, and yes I have had a few of them crack