First contrast reduction mask. How to control dust?

[SeanEsopenko]

So I did my first contrast reduction mask. Without the reduction mask Fuji CA paper was just too contrasty, blowing out the sky almost completely and rendering the upper-left tree into complete darkness. a 300 dpi scan of this image with the contrast reduction mask can be found here. My very first try (and a failure) can be found here.

I exposed Ilford FP4+ 4x5 film under the enlarger with white light (0,0,0) on my Omega dichroic II's "low" setting for 1 second. I exposed 5 negatives from f 5.6 to F22 to see the effect and after some prints with a few of them I liked the F22 shot the most. They were tray developed in D76 1:1 for 9 minutes (about iso 50 according to ilford's documentation).

I feel quite liberated now that I know how to do masking and while the registration wasn't perfect it's not as intimidating as I thought it was. The only serious trouble I'm having is dust exposing into the contrast mask. I used a rocket blower like crazy on every single surface (colour negative, b&w negative, plexi glass for weight) but dust was exposed into every single reduction mask I made.

Any advice on how to control the dust?

[Mark Woods]

I keep a small tank of nitrogen gas in my dark room to load film and for negs that go into the enlarger or contact printer. I haven't had any problems. I have the regulator set at 90 lbs/psi with a blower nozzle. I haven't had any problems with dust since I've done this. It's pretty standard in the Motion Picture industry pre digital. ;-)

[Drew Wiley]

Same rules as controlling dust with any other kind of film operation. There are any
number or previous threads about it. Sponge things down in advance. Don't wear
clothing like cotton that generates lint. I wear a pure dacron clean-room smock.
An electrostatic air cleaner and small halogen machinist's inspection light are at the cleaning station. I wear reading glasses. The air coming off my compressor in an
adjacent room is triple-filtered. When the masking film comes out of the paper safe
it is blown off before registration. Contact frame glass and neg carrier glass is
thoroughly cleaned before every work session, etc, etc.

[ic-racer]

I exposed Ilford FP4+ 4x5 film under the enlarger with white light

With the lens in place? That is producing collimated or semi-collimated light that will show any dust on all surfaces (both sides of glass and both sides of original and on top of the exposed negative.

Try a diffuse source. Like just taking the lens out or even putting the mixing box right on the negative sandwich for exposure.

[jeroldharter]

What method are you using for registration?

[Drew Wiley]

The enlarger lens just needs to be de-focused a bit; no need to remove the lens. A
3-mil or 5-mil frosted mylar diffusion sheet between the original and the masking film
will supress the finest dust anyway, and will be easy to clean with a blower. Similarly,
if the contact frame glass is not anti-Newton, a piece of diffusion sheet here will provide that characteristic, plus supress any fine dust or scratches on the glass itself. Practice makes perfect. But it's good to see folks experimenting and improving their images.

[SeanEsopenko]

What method are you using for registration?

I registered by hand on a light table with an 8x loupe. I'd like to avoid the cost of a registration punch and I have a very good eye anyways. It appears as though B&W negative expands/contracts at a different rate due to heat compared to the colour negative. The b&w negative needed to be kind of "stretched" before I taped them together to get the image to line up at all corners. Then when it cooled as I was putting it in the glass carrier to enlarge it it kind of "popped" as it cooled.

Next time I'll be taping the colour negative to a piece of acetate slightly larger so I have a better surface to tape the B&W negative to when registering.

The enlarger lens just needs to be de-focused a bit; no need to remove the lens. A
3-mil or 5-mil frosted mylar diffusion sheet between the original and the masking film
will supress the finest dust anyway, and will be easy to clean with a blower. Similarly,
if the contact frame glass is not anti-Newton, a piece of diffusion sheet here will provide that characteristic, plus supress any fine dust or scratches on the glass itself. Practice makes perfect. But it's good to see folks experimenting and improving their images.

the enlarger lens was defocused a fair bit. Do you mean place the diffusion sheet between the B&W masking film and the colour negative or place the diffusion sheet on top of the two negative films? Do you think "reflection control" glass is frosted enough? I can get that stuff for real cheap (wife has a framing shop).

Same rules as controlling dust with any other kind of film operation. There are any
number or previous threads about it. Sponge things down in advance. Don't wear
clothing like cotton that generates lint. I wear a pure dacron clean-room smock.
An electrostatic air cleaner and small halogen machinist's inspection light are at the cleaning station. I wear reading glasses. The air coming off my compressor in an
adjacent room is triple-filtered. When the masking film comes out of the paper safe
it is blown off before registration. Contact frame glass and neg carrier glass is
thoroughly cleaned before every work session, etc, etc.

I'll bring my ionizing filter to the darkroom and get myself one of those anti-static brushes. When the lights are out to handle the B&W film I can't see what I'm doing so the suggestion of reading glasses & such is not going to help much. My enlarger is in a little niche so sponging/wiping everything down for dust is a good idea. I think I had the ventilation running and it's close to the enlarger cubby which probably kicks up dust. Maybe I can give dust 10 minutes or so to "settle" after wiping & mopping before I turn out the lights and make the contact sheets.

Thanks everyone for the suggestions. I have a lot to work with now the next time I do this. It's a shame I already ordered Porta 160 film, expecting to have fewer problems with contrasty negatives. After I saw the masked Ektar I just loved the saturation level that I don't think I'll get with Portra. I guess I'll see...

[bob carnie]

Raise the humidity in a clean room Sean.

[jeroldharter]

If I were going to the time and effort to mask color prints in a darkroom, I would buy a masking carrier if I could afford it. Makes life much easier, less film handling, repeatable, easier to contain dust.

[Drew Wiley]

The two films will stay dimensionally stable if they're both polyester rather than acetate. Porta and Ektar sheet films are estar, so are most black and white films suitable for masking, such as FP4 or TMax. But using polyester tape to put them together rather than ordinary acetate Scotch tape will help too. The frosted mylar always goes between the original and the unexposed masking film to diffuse the image a bit. A second sheet can go between the original and the contact glass if needed. You don't use one when printing. If the film is popping during exposure it means you need to print using a glass carrier (which I do 100% of the time). You can experiment with different glass types, but etched picture glass will probably show up as a pattern in the print; optically-coated framing glass might work, but it's best to acquire real anti-Newton carrier glass from someone like Focal Point. If you do much masking you'll definitely want to acquire a punch and matching contact masking glass. But light box registration is fine for just learning the basics.