Has anyone ever baked a lens in an oven before? (Lens Repair - Epoxy Removal)

[FalseDigital]

I picked up a voigtlander color skopar 21mm f4 lens (M-mount) in Japan from a junk bin for 4,000 yen. The lens elements themselves appears to be in pretty good shape (ignore the spots, they are just from splashed alcohol and came right off) ....except there a few strange things.

It's been permanently epoxy'd (I'm guessing it's epoxy) to a Fujfilm F mount adapter and the original M-mount tabs have been grinded off. The focusing ring has been removed and it has also been epoxy'd so that it cannot be focused. It's set at infinity permanently. I would like to be able to focus it again and I'd like to be able to reapply it to a proper mount.

Here are some photos to show you what I mean:

I managed to pry it from the mount which it was simply glued to. However there is no way I can get the ring to turn. I was wondering....would it be possible to bake the lens in the oven to loosen the glue?
Would this destroy the glass if I did so?
Has anyone ever attempted to do something crazy like this before?

Also, before anyone says...I have already tried Nail Polish remover and Alcoohol, neither of which affect the glue one bit. So that's why I'm guessing it's epoxy.

Any help would be appreciated! Cheers!

 

[B-9]

Bake it!

Worth a try.

 

[FalseDigital]

But would it shatter the glass if I did? That's the issue.

 

[davidnewtonguitars]

I don't think the glass will be the problem.
If it is 5 minute epoxy it doesn't take very much heat to soften it, much more heat for regular epoxy. But which ever type it is, the paint is will likely bubble before the epoxy softens.
Can you get a heat gun to point the heat at the helicoid area? I think a blow dryer could soften 5 minute epoxy.

 

[02Pilot]

You want much more directed heat. As noted, baking is likely to destroy the finish on what remains. Try a soldering iron or a heat gun.

That said, that's a lot of work for a lens that you can easily use in many (most?) situations locked at infinity. I'd be inclined to figure out the mount and leave the focusing alone, but that's just me.

 

[retinax]

the lens certainly has some cemented elements? You'd risk the cement breaking down or bubbling or whatever. I wouldn't apply heat. Unless you can dismantle the lens and bake only metal parts, is that not possible?

 

[B-9]

Most cheap heat guns come with multiple reflectors to pinpoint the heat.

The glass will not crack unless you decide to quench them in cold while still hot.

I would let the paint bubble off personally.

I did not consider cemented elements... those will surely bubble up in a oven.

I've separated cemented telescope objectives in the oven for cleaning then just oil spaces them afterwards... so maybe no oven!

 

[Steve M.]

An oven is simply going to bake the epoxy on that much harder. What you have is what you got, unless you can take a Dremel tool and cut out the epoxy, which I doubt would work.

 

[rjbuzzclick]

You could also try a food dehydrator. That would give you a stable temperature that's lower than an oven could do (< 200f). I used to use one a lot to bake old analog reel-to-reel tapes to restore them.

 

[peterm1]

Not sure of the optical layout of this lens but if any elements are balsamed the balsam will melt though heat. While this may not matter if the lens is allowed to cool slowly after any shock while soft could possibly decenter them, though this may be less likely to happen if they are still held firmly in their mounts. (Heating old balsam is sometimes done when old lens elements need recementing - the cemented elements are heated, the balsam melts and the elements then pressed together and reset. However this is done with the glass removed from the lens mounts. Some people here have reported doing this in an ordinary kitchen oven but at quite low temperatures.) Having said this metal expands differentially from glass when heated and cooled so I am not sure how this would play out so there are clearly some risks to be ware of.

Why someone would gum up a perfectly good lens in the way you have described is a mystery to me. Focusing the sun's rays to burn ants perhaps?

There are some ideas on removing cured epoxy at these three links.

https://www.doityourself.com/stry/8-tips-for-removing-epoxy-adhesive

https://www.wikihow.com/Remove-Epoxy

https://www.microtonano.com/TIN-Removing-Cured-Epoxy.php

 

[x-ray]

But would it shatter the glass if I did? That's the issue.

I had a Gundlach Turner Reich tripple convertible view camera lens that the balsam between the elements had deteriorated. I took it to an optical designer / builder to be repaired. The person separating the elements was using heat, as he should, but the glass heated unevenly and the lens cracked.

You always run the risk of damaging or destroying the lens.

Before I heated it I'd try a few other solvents like toluene and acetone. If you try this consider it could damage the coatings if you get it on the glass. Also do it in a well ventilated area and use nitrile gloves. Acetone and possibly toluene is absorbed through the skin and can be toxic. Soak the epoxy for a while. It may be the you need to apply the solvent to the glued area with a glass eyedropper being careful to avoid the glass.

Google "remove cured epoxy" and see what you find.

Good luck!

 

[FalseDigital]

Thank you everyone for the feedback!

I hadn't thought about cemented elements...that makes sense that heat could potentially destroy them. I tried to remove all of the elements however there is one left that cannot be removed. See photos below:

I don't have a heat gun...so I was thinking of trying to bake this...with just the one element left inside. It can't be removed because the screw that holds it in place is also glued tight like the focusing ring.

So...votes?
Yes, try it! No, you're crazy!

 

[Huss]

Do it! Do eeeeeeet! I hope for the best but this is too much fun, and what ya got to lose?

 

[leicapixie]

I am not happy "baking"!
I have used acetone(hardware store" variety,not beauty counter.
Cleaned up a vented lens-hood for my 50mm Summicron.
Use a brush and coat the epoxy.
It will soften, over time.

 

[FalseDigital]

I can't coat the epoxy, it's inside the screw which cannot be unturned.

 

[FalseDigital]

Update!

So I used a soldering iron and was able to somehow loosen the mount. Now all the elements and aperture have been completely separated. Now just the focusing screw is left. I put that in the oven by itself. *fingers crossed*

 

[FalseDigital]

Baking did nothing. Ugh.

So now I've got it sitting in bowl of nail polish remover.
I need to find some acetone, sadly it's a bit hard to get in Thailand. I have to go to a chemistry store to find it. Maybe that will help....but at least I have it separated from the elements and aperture!

 

[Huss]

Is acetone better than using petrol?

 

[Mr_Flibble]

Nail polish remover is Acetone as far as I know.

@Huss; Acetone is generally more aggressive.

I've had luck baking lenses (melting and resetting/removing the cement) and focusing helicals (melting hardened grease like the notorious Agfa Green Goo)
I set the oven to the lowest setting (100-110C) and let the item heat up inside it for up to 10 minutes max.

 

[FalseDigital]

PROGRESS!!!

So I decided to pour boiling hot water in with the nail polish remover. I let it sit for a few minutes and then was able to FINALLY unscrew it. Now I'm letting it sit to try and get rid of the leftover gunk that's still in the screw threads. There is still an outer ring that it's attached. That particular ring does not have any place I can grip it with a tool...so hoping if I leave this sit for a few hours it will somehow get inside and loosen it up.