How I did it: new balsam for a sick RR

Acetone is a very good solvent.
But it is something of a problem child outside of a laboratory.
It boils at about 56 deg C, Has a flashpoint of minus 15 deg C (can cause explosions above -15 C even when mixed with water!).
Xylol (xylene) boils at 140 deg C and has a flashpoint of plus 56 deg C.
Methylene chorlide (dichor-methane) boils at around 40 deg C but is not inflammable alone - it burns at around 600 deg C.

The vapour pressure of Xylol (amount of xylol in the air above a vessel) will aways be less than acetone.

All are nasty solvents - healthwise - short and long term.

Dear moderators!

Someone has just asked me what has happened to the photos which I have uploaded in this thread. The whole thread seems rather less than useful in its present state!

Interesting thread. Methylene chloride will go right through most reasonable lab gloves like what some of us use for developing film. i.e. medical exam gloves. Even two layers of latex gloves are no help. I've tried. I used to DCM by the multiple gallons when I was a researcher in the pharmaceutical world. nitrile gloves are better but the thickness of the gloves required to truly exclude DCM mades handling delicate lenses troublesome. I would second the thought that acetone is a wonderful solvent, but it is very flammable/explosive and finds pilot lights..., it is less toxic (possibly) than benzene, toluene, xylene and methylene chloride/dichlormethane (synonyms). I think we would all be wise to limit chemical exposure to photographic chemicals and solvents etc. but also not be too phobic about it. Lots of chemists used to work without gloves, without fume hoods, and wash their hands in 1:1 acetone:benzene and lived to ripe old ages. Sure, there's a subset that died young, but most of those stories I've been able to track down involved far more toxic molecules than common or uncommon solvents. Also, the formation of formaldehyde from DCM? I'm skeptical your body has the biochemistry to remove the first chlorine atom. Sure, I can do it in the lab, but the body, I don't know. Also, your body can and does make acetone in some situations (high protein, low carb diets for instance). Again, I'm not suggesting we be too cavalier with these materials, but also, let's not be so phobic either. The universe is made of chemicals, a skiff of electromagnetic energy, plasma, and a lot of vacuum. About picking solvents for tasks: in general molecules of larger size are dissolved by molecules of smaller size with similar chemical characteristics. Ex. Sugar molecules have a "coating" of what are arguably 2/3 of a water molecule. Sugar dissolves well in water. Table Salt is ionic and water has strong (for a covalent molecule) charge separation and dissolves table salt. Candle wax is mostly hydrocarbon and kerosene, a sorter length hydrocarbon, is pretty good for getting candle wax off of surfaces in church. And kerosene can be gotten rid of with isopropanol and or some soaps which won't touch candle wax. I think Canada Balsam is a resin from a coniferous tree, probably distilled/waste from making turpentine. So, it's a hydrocarbon or a lightly modified one (maybe some oxygen atoms?). It's not surprising that hydrocarbons, like toluene and xylene act as solvents for it. Gasoline and kerosene and diesel and Coleman fuel might also work but are much more flammable and the peculiar nature of benzene/toluene/xylene of having an "aromatic" ring in them may also help in getting the Balsam dissolved. DCM is a chlorinated hydrocarbon. It has a smidgen more polarity than true hydrocarbons and a certain amount of "squishiness" of electron density due to the 2 chlorines that mimic, in a way, the aromatic ring in Xylene's "squishiness" that also make it make sense for getting Balsam apart. I'm suspicious that Canada balsam may have a little solvent in it to start with and if it gets too "stiff" adding a tiny amount of very pure solvent back may restore it to workability. On the other hand, it might be cured by polymerization like the oils in oil paints but that would tend to preclude getting it apart with solvents. Once molecules get to a certain size (in general) you can't solubilize them i.e. starch is a polymer of sugar and isn't soluble in water.

The pictures would have very useful.

Quote:

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Originally Posted by Steven Tribe

Dear moderators!

Someone has just asked me what has happened to the photos which I have uploaded in this thread. The whole thread seems rather less than useful in its present state!

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I do hope the pics return. Would like to re-read.

I'm thinking that they (pictures) must have, were originally posted on a different site and have expired on that different site, like a lot of the photo's here and on other web sites, too bad.!!

No. They were uploaded to LFPF.

Well lets hope the mods will be able to retrieve them.

Attachment 163791

The picture above is a shot of the lens as removed from my 1890 model Blair 4x5 detective camera. The lens is suffering from severe balsam separation. I decided to try and make the repair myself, inspired by this thread. Since the original thread is older, it seems the photos have disappeared. So, during the process of restoration, I am posting a few new pictures just in case this is helpful in the future to another faced with the same lens problem.

Attachment 163792

Slowly bringing the lens up to temperature in a pan of water.