best materials for making darkslides/septums

[Scott Davis]

Anyone have any recommendations as to what material to use for making darkslides and septums? Also, could you specifically address what thickness of material should be used?

[Oren Grad]

What Alan Brubaker says (http://www.filmholders.com/filmho1.html)

What S&S says (http://ssfilmholders.com/?page=film_holders)

[Harold_4074]

"Phenolic'" in this context usually means a composite having a phenolic resin binder; try Garolite Grade XX in opaque black, available from McMaster-Carr.

The last holders that I bought new had slides which appeared to be made of a pebble-surfaced thermoplastic, probably polypropylene, but all of my older holders seem to be identical to the paper/phenolic Garolite, so that is what I used to make a set of apertured slides for film testing.

[Colin Graham]

For what size holders? I made my 5x12 holders with 1/16 for the septums and 1/32 for the darkslides. It takes a lot to snap the xx garolite from McMaster, so I'd be tempted to use the same material for holders up to 10x12, maybe even 11x14.

[Scott Davis]

The camera in question needing holders is a 12x15. I'm thinking of using the 1/16" for the slides and then maybe the 1/8" for the septum, just to make sure it is rigid enough. I've got some room to play with since the camera originally took bookform plate holders (it's a Watson from about 1880).

[Colin Graham]

Hmm, well I think I'd still be tempted to try the lighter weights, since I hike and obsess about weight. Just thinking out loud, but since the septum is always supported on all sides, 1/16" might still be plenty there. And if you make a somewhat pronounced concave cut on the leading edge of the darkslide so it doesn't hang up at the groove in the film gate, along with a deeper groove to make sure it's still lightproof, 1/32" for the darkslides might work as well.

I wish I still had some larger samples laying around here to see how floppy a sheet that size might be. The stuff is much more rigid than you would think, even the 1/32 stock. Anyway, might be worth getting some to experiment with.

[chris_4622]

Colin,

What did you use to cut the 1/32" groove? I looked at having some tooling made but they wouldn't guarantee them from run out.

chris

[Colin Graham]

I have a micro milling machine, which uses a mandrel that can accept a variety of very thin, small diameter blades.. called slitting saws, iirc. It's the main reason I got the mill, I couldn't find a way to cut grooves that thin with traditional woodworking tools. The mill and arbor and several blades were the cost of one new custom holder at the time, so it was a fairly easy purchase to make.

[Scott Davis]

The weight isn't quite as much an issue as I expect I'll be using this camera in the studio more than 90% of the time. Sounds like a good idea though to order a few sheets in the required size first.