Hasselblad light seal replacement question

[Theo43]

When you take the face plate off a film back and look at its (the face plate's) inside, you see a channel that runs around the perimeter of the 6x6 hole. On three sides this channel appears to be about 1 mm deep and 1mm wide; on the fourth side the channel is about 2mm wide and is deeper on the outside side than on the inside side. When I took the face plate off a back this morning the three narrow channels were clean, but the wide one (which is where the dark side is inserted) had some residue/gunk in it. I have cleaned the wide channel out but, clearly, there had been something in it which, presumably, I should now replace. Any suggestions as to what might work for this application? Thanks,
Ted

 

[jeffreyg]

Call Hasselblad and order the light seal kit. It takes a couple of minutes to install another one. Be sure to clean the "gunk" off it is the remnants of the old seal. You can find illustrations on the web

 

[Theo43]

I did not make myself clear. Installing the light seal itself is not a problem as I have all the necessary stuff. It is the channels on the inside of the face plate that I refer to, and wonder what to use in the 'wide' one.
Ted

 

[jeffreyg]

I recently replaced on but did not notice a difference in the channels. I just unscrewed the plate, installed the new seal and replaced the plate. The kit included a "foam" material and mylar strip. It had a different shape on each end and only went in one way. Once I replaced the plate I tested it with a roll of film and there was no longer a light leak. I don"t recall the web site with illustrations but found it through an APUG forum. Try a search through prior medium format threads. It was very simple to do and took 5-6 minutes start to finish.
Hope this helps.
Jeff

 

[Q.G.]

There is some black, thin, velvet like material in the long channel.
Any such material will do, provided it is not too thick.

If you would want so, you could order some from Hasselblad. Part number is 12295, and they call it (because it probably is) "Ribbon".
But i'm sure it will be far too expensive if you get it from Hasselblad.

 

[jeffreyg]

I found the web site: hasselbladhistorical.edu/HT/HTSeal. aspx

 

[Q.G.]

".edu"??? The site is in quite a few domains, but has yet to go educational.

Try http://hasselbladhistorical.eu/HT/HTSeal.aspx

But the OP didn't ask about how to change that seal.

 

[sandermarijn]

Q.G., the last time I replaced the light seals of one of my two A12's I felt that the ribbon looked a little flat/flattened, not 'cushiony', if you know what I mean. Should it be like that? Is the ribbon as critical as the light seals themselves? Should you replace it every now and then? Thanks, Sander.

 

[Q.G.]

I don't know: i have backs in which the ribbon is hard, with all of the nap worn off, and still no problem. I doubt that many backs ever get this ribbon replaced at all
The foam seal is much more important indeed.

But i do think i really should replace the ribbon: no need to take unnecessary risks.

 

[sandermarijn]

Thanks Q.G.- I will leave mine the way they are. I may mess it all up otherwise.

 

[Theo43]

I am thinking a strip of medical cloth tape might work. Since the dark slide goes back and forth over this, one does not want anything that could break down and send debris into the film area. Thoughts?
Ted

 

[Q.G.]

I don't know that stuff, but yes: it shoudn't fray or fall apart too easily.

 

[brucemuir]

Wait,
one time I found one of those ribbons (it was pink colored) and I assumed that was what someone made to replace the foam seal we use now.

Is the ribbon an extra part that is supposed to be in there beside the one foam piece and cut mylar piece?

I've never seen mention of this 3 part until now? ? ?

 

[Mark Fisher]

I bought replacement seals from an ebay vendor for $12. As previously described, it is a foam "spring" pushing up on the folded mylar strip. Works perfectly. I wouldn't trust using velvet or something similar. I wouldn't trust a piece of velvet or similar for very long. The light seal area is much narrower than a 4x5 darkslide so the light sealing needs to be that much better.
There was no third part in any of the backs (3 - A12) that I've replaced seals in.

 

[Philippe-Georges]

When I replace a light-seal, I used to clean the small felt ribbon with some lighter fuel or Isopropyl alcohol. This felt takes up a lot of dirt, grit and fat from you hands handling the slide, after cleaning, then it is a little more flexible.

Philippe

 

[Q.G.]

Wait,
one time I found one of those ribbons (it was pink colored) and I assumed that was what someone made to replace the foam seal we use now.

Is the ribbon an extra part that is supposed to be in there beside the one foam piece and cut mylar piece?

I've never seen mention of this 3 part until now? ? ?

The strip of cloth, ribbon, is behind the face plate of the magazine (the thing you take off and put to one side when you change the foam, and never look at. Until you put it back on again, and then you'll not likely see/look at it).

It is not, Mark, a replacement for the foam. And it is (or should be) in all of the backs you changed foam in.

It is not a thing that needs changing much (if at all). Which is (one reason) why it is not easy to change: glued in.

 

[Theo43]

I think Philippe's observation (dirt, grit and fat) tells us something, namely, the likely purpose of the thin ribbon is to wipe crud off the film-facing side of the dark slide as it is inserted into the film back. It may not have any light sealing function, but should be left in place or replaced in any event. I sold my RB67 gear after buying Hasselblad gear last fall, and only this morning thought to look at an RB light seal kit I had got from Jon Goodman, which contains a variety of useful materials including a piece of very thin (1mm) self-adhesive black velvet that is perfect for this application. The kit also contains self-adhesive foam in several thicknesses; I decided on 2.5mm for the Hasselblad film back. One could likely order sheets of these materials directly from Jon Goodman. http://www.kyphoto.com/classics/sealreplacement.html

 

[Mark Fisher]

The strip of cloth, ribbon, is behind the face plate of the magazine (the thing you take off and put to one side when you change the foam, and never look at. Until you put it back on again, and then you'll not likely see/look at it).

It is not, Mark, a replacement for the foam. And it is (or should be) in all of the backs you changed foam in.

It is not a thing that needs changing much (if at all). Which is (one reason) why it is not easy to change: glued in.

Hmmm....I didn't get it in the kit. I wonder whether the Hassy kit includes it.

 

[Ira Rush]

Hmmm....I didn't get it in the kit. I wonder whether the Hassy kit includes it.

Mark,

Interesting... very interesting...

I bought about 5 sets (directly from Hasselblad, NJ ) about a year ago. The only two items included were the foil and the foam, ... No "ribbon".

And to tell you the truth, in all the years I've been replacing my seals and traps, I never noticed that ribbon either!

 

[brucemuir]

Yep, I've only encountered the ribbon once but I did save it...

My guess is it doesn't get replaced at some point and my backs don't have this piece at all (unless they are glued on and I didn't flip the back plate over and notice it).

I have at least 3 different generations of backs from a 12 w/peephole up to an A12 of some iteration.
On all the ones I resealed I don't think any of them have this part now and they don't leak.

This has certainly been educational and I thank QG for clearing it up.

 

[Andrew Moxom]

I will also add that anything but the OEM seals is a false economy. While other vendors maybe cheaper.. I've run into issues using IR film using non OEM seals. Think about it, the OEM ones have a foil where as the off brand ones just have foam and mylar. Why risk it?

 

[Q.G.]

Hmmm....I didn't get it in the kit. I wonder whether the Hassy kit includes it.

No, no, no. It's not in the kit!

"It is not a thing that needs changing much (if at all). Which is (one reason) why it is not easy to change: glued in."

You only should worry about it when, as happened to the OP, you notice that it starts falling out in a crumbled mess.

 

[Q.G.]

I will also add that anything but the OEM seals is a false economy. While other vendors maybe cheaper.. I've run into issues using IR film using non OEM seals. Think about it, the OEM ones have a foil where as the off brand ones just have foam and mylar. Why risk it?

Well, perhaps.

The bit that needs changing most is the foam.
And it's not false economy to find and use a cheaper alternative bit of foam. Everytime i change a bit of foam, i spend about ... oh what? ... $0.02?
Never a problem.

I have yet to find a good alternative for the foil envelope.
Could be that the original is IR-proof, i never tested it. So perhaps the often suggested alternative, a bit of exposed and developed BW film (the leader of 35 mm film) would do.
I don't know whether it is suited though, whether it foulds easily enough, and whether it can withstand the sharp edge of the slide any better than the foam it is supposed to protect against that very same sharp edge of the slide.

 

[Q.G.]

I think Philippe's observation (dirt, grit and fat) tells us something, namely, the likely purpose of the thin ribbon is to wipe crud off the film-facing side of the dark slide [...]

If so, a shame that it is on the other side, brushing the side of the slide facing away from the film.

 

[Theo43]

If so, a shame that it is on the other side, brushing the side of the slide facing away from the film.

My bad Q.G., it does indeed brush the slide's side that is away from the film; thanks for the correction. So much for that hypothesis!

I have tried developed B&W negative in place of the foil but it is very stiff and, worse, tends to tear at the square notches, so I have stayed away from using this alternative.