For you chemists - a Leica shutter repair problem

[Vickko]

Hello all. I've been CLA'ing my Leica IIIf, and it may turn out it isn't a mechanical problem at all.

It may be my repair of my pinholed shutter is acting up, in the humidity.
I read the label of the fabric paint that I used, and it says "Fix at 40 deg C for 5 minutes".
I think my fabric paint is getting sticky, and when it is rolled up overnight, it sticks to the adjacent shutter material.

In any case, I'm letting it dry.

I can't bake the camera at 40 deg C (actually, maybe I could).

But can you think of a chemical method to "dry it out"? e.g. dissolve the water and evaporate it away? Any recommended chemicals to try this with? Alcohol?

Thanks in advance.
...Vick

 

[cnphoto]

I can't bake the camera at 40 deg C (actually, maybe I could)

yes, you could. it may potantially damage the vulcanite covering, but that is adhered to the camera using a greater heat than 40C - so it would probably be ok. low heat, camera on a baking tray.

turn it to brown both sides accordingly and salt/pepper to taste 😉

 

[Freakscene]

The solvent in the adhesive paint is unlikely to be water or alcohol based. I think taking the shutter assembly out of the camera and heating it as the paint instructions suggest is a good idea. I can't remember what the inside of a Leica iii is like, but if you can get the shutter away from the range finder it would be helpful. The old cements in the prisms and mirrors may separate if heated.

Marty

 

[xayraa33]

Clean off the fabric paint and apply several thin separate coats of artist acrylic paint like Liquidtex Mars Black Soft Body.

 

[willie_901]

From a chemist's perspective it is possible the 40 deg C is required to initiate a chemical reaction in the fabric paint. The problem may have nothing to do excess solvent.

I suggest you very carefully heat the painted area with a small heat gun. Obviously the heat gun must be at low power (heat and air flow). Perhaps you could rig something to the nozzle that would both bleed off excess air pressure and focus the air flow. Whatever you do, experiment to make sure there is not too much heat or air pressure. Alternately a small light bulb (AC or DC) may get warm enough to selectively heat the painted area. Again, to avoid damage, you will need to experiment before actually heating your shutter.

Best wishes

 

[maddoc]

Reaction activation energy or solvent evaporation, in either case elevated temperatures help. I would suggest to remove the mechanics form the body (if possible) and then repeat the paint drying procedure with a hairdryer that can be regulated to moderate temperatures. If you carefully warm the shutter this way it should work. I would strongly suggest no to experiment with any solvents because the chemistry involved in the reaction will be altered ...

 

[Murray Kelly]

Actually 40 C isn't all that hot. Body temp is 37 C.
I suggest you open up the camera so you can see the repair site and direct a hair drier onto the paint area. Don't get carried away, tho, those hai driers can make things too hot to handle if you get too close.
Murray

Hello all. I've been CLA'ing my Leica IIIf, and it may turn out it isn't a mechanical problem at all.

It may be my repair of my pinholed shutter is acting up, in the humidity.
I read the label of the fabric paint that I used, and it says "Fix at 40 deg C for 5 minutes".
I think my fabric paint is getting sticky, and when it is rolled up overnight, it sticks to the adjacent shutter material.

In any case, I'm letting it dry.

I can't bake the camera at 40 deg C (actually, maybe I could).

But can you think of a chemical method to "dry it out"? e.g. dissolve the water and evaporate it away? Any recommended chemicals to try this with? Alcohol?

Thanks in advance.
...Vick

 

[xwhatsit]

40°C is nothing -- it gets that hot regularly in Australia during summer anyway. I'm sure there's a few Australian screwmounts still around.

Direct heat with a hairdryer would almost be worse in a way, wouldn't it? At least by heating the whole camera to 40° you're heating it evenly.

 

[wolves3012]

yes, you could. it may potantially damage the vulcanite covering, but that is adhered to the camera using a greater heat than 40C - so it would probably be ok. low heat, camera on a baking tray.

turn it to brown both sides accordingly and salt/pepper to taste 😉

If you've ever tried removing vulcanite, you might want to think again on that! Needs about 200 degrees to soften it. I've resorted to a blowlamp to get the stuff off (not recommended on a complete camera!).

 

[Vickko]

Yes, this might be the best suggestion.

So do you think high humidity would have made the water based fabric paint moist again?

And how could it be water based fabric paint; wouldn't it have washed out, if it were supposed to be used for t-shirts and the like?

Or is that what the heat conversion was supposed to do, to render it waterproof?

Vick

Clean off the fabric paint and apply several thin separate coats of artist acrylic paint like Liquidtex Mars Black Soft Body.

 

[le vrai rdu]

Hello all. I've been CLA'ing my Leica IIIf, and it may turn out it isn't a mechanical problem at all.

It may be my repair of my pinholed shutter is acting up, in the humidity.
I read the label of the fabric paint that I used, and it says "Fix at 40 deg C for 5 minutes".
I think my fabric paint is getting sticky, and when it is rolled up overnight, it sticks to the adjacent shutter material.

In any case, I'm letting it dry.

I can't bake the camera at 40 deg C (actually, maybe I could).

But can you think of a chemical method to "dry it out"? e.g. dissolve the water and evaporate it away? Any recommended chemicals to try this with? Alcohol?

Thanks in advance.
...Vick

a desk lamp with a 60 W bulb will bake it

 

[Murray Kelly]

40°C is nothing -- it gets that hot regularly in Australia during summer anyway. I'm sure there's a few Australian screwmounts still around.

Direct heat with a hairdryer would almost be worse in a way, wouldn't it? At least by heating the whole camera to 40° you're heating it evenly.

Not too regularly. But more than Auckland!😉
Leaving it on the dashboard for a few hours would achieve the same result. 40C is quite comfortable to the touch.
Murray

 

[xayraa33]

Yes, this might be the best suggestion.

So do you think high humidity would have made the water based fabric paint moist again?

And how could it be water based fabric paint; wouldn't it have washed out, if it were supposed to be used for t-shirts and the like?

Or is that what the heat conversion was supposed to do, to render it waterproof?

Vick

The fabric paint probably did not cure as the temperature was not 40 deg C or higher and if it was applied in a single thick coating it would take a while at that heat level.

Vic, I would clean off that fabric paint as much as I could with what ever solvent that can do the job without destroying the rubberized shutter cloth (you might have to run some test experiments on a piece of scrap shutter cloth from a parts FSU camera) and apply light acrylic black artist paint in a thin layer and let dry for a few days. Repeat a few times to get a light tight seal on the offending shutter curtain(s).

 

[Vickko]

It's baking, above a light bulb. Excellent suggestion, le vrai rdu, by the way.

And it's looking good. 🙂