Light sealant in Bolex still very soft

[Jon O'Brien]

I bought a non-reflex Bolex the other day. Going by the outside alone it doesn't look like it's been used much.

However, on opening up the film compartment it looks like it's been dismantled/opened up for some reason. Perhaps it seized up after decades of no use, and just needed an oiling.

Whoever did it wasn't completely fastidious as there are quite a few finger print marks on the inside of the door/lid and the light sealant material that looks a bit like a continuous bead of black silicone sealant that is put around the join between the back of the film compartment and the side walls of the camera looks a bit messily applied in one or two places. Though it's not too bad.

But what has me concerned is that this black silicone-like stuff that looks like very thick paint seems not to have dried, or 'set'.

It has a very tarry/greasy feeling (where I touched a widely-applied smear of it). Is it okay/normal for this black light sealant gunk to still be very soft and greasy/tarry? I think the camera should be okay, as the film doesn't touch this part of the camera. But I thought I should check to see what the experts here at cinematography.com think.

[Tyler Purcell]

Got pictures? 

 

[Jon O'Brien]

There's not much to see, Tyler. Just like I described. The bead of black stuff looks pretty much just like it normally looks like on a typical Bolex, except it's smeared a bit widely in two places. I touched it there, and it smeared like black grease. I didn't disturb the light 'seal' (I assume that's what it's there for). I will see if I can get some pics.

[Simon Wyss]

Soft sealant isn’t bad per se, it can be read as a good sign actually because somebody may have taken care of the mechanism. Dry hard original mastic seal tells of decades of no service.

I use an acetic-acid base sealant that dries within a day or two. It becomes rubbery soft and dull in appearance. If someone proofs the main plate to the shell, nothing should be smeared around in the film compartment. It’s part of the job to wipe that clean.

Last year I have prepared some organic sealant from Greek mastic, turpentine, and soot but it got too thin. Need to buy some more mastic.

[Jon O'Brien]

That's reassuring to know.

It's an H16 M. A very nice looking camera. I just got it out, wound it up fully, and ran it without film at 24 fps. It ran for a fraction over 30 seconds on one wind and sounds very smooth-running so perhaps I got a good one. Then I tried the Rex-5 and it ran for exactly the same time. I guess if pulling film through the mechanism they don't run as long.

I will still get some pictures here. Been very busy.

[Simon Wyss]

The run length is constant, given by a gear mechanism. Without that the spring could be wound completely on itself with the danger of tearing it off the hook inside the barrel and unwound until laying on itself outwards. I have used an H-16 the stops removed, the spring pulls just shy of the double frame number, i. e. around 54 seconds at speed 24. Please acknowledge that the speed numbers on that black dial aren’t very precise references, one is best advised to set speed by running full lengths with film while observing a stop watch. First you determine the number of frames pulled through on the counter. It varies a little among examples but remains the same with one camera.