I'm interested in nitrogen burst agitation, and what advantages there are to this form of development if any for B&W 4x5 film development. I am considering this form of development due to the need to develop high quanities of film, somewhere between 25 to 100 sheets per darkroom session. My questions involve whether nitrogen systems maintain constant flow or intermittent per a normal inversion schedule? I have the capabilites to construct such a system but require input as to nitrogen header and outlet sizes, rate of flow, and timing if necessary. I also have a question as to film spacing. Developer replenishment will be manual at first, but I can develop a semi automatic system.

If the above is impractical, would a simple liquid pump system suffice? My idea is for a table top system using stainless clip hangers. I am not interested in Jobo, tube or tray development. Any practical ideas or paths for research are appreciated.

-- Wayne Crider (waynec@apt.net), February 23, 2001

Answers

Wayne, Making a plenum to distribute the nitro isn't all that hard. What you need to do is to make it out of fine hard tubing that you can make pin holes into. A weighted basket will help to keep it to the bottom of the tank and distributed evenly. Keep the bursts intermittent similiar to the regular agitation you would do by hand. You will have to experiment to see what is good for the system. A good way to do this is to shoot maybe 20 sheets of a grey solid background (copy stand works great) and process several at a time. If you are doing deep tank, put a few at the bottom near the plenum and a few on the top to test the turbulance top to bottom. Also, shoot a grey scale and either read the densities top to bottom or have a pro lab give you read outs. My burst was a 5 sec burst/ 20 sec. rest. At least this is a time you can start with.

-- Scott Walton (f64sw@hotmail.com), February 23, 2001.

One last thought... make sure you can get deliveries of Nitrogen!

-- Scott Walton (f64sw@hotmail.com), February 23, 2001.

Finding a timer won't be easy, but they are out there if you look hard enough. Find a copy of Kodak Pub. No. E-57 [no longer available from Kodak]. It should answer most of your technical questions.

There are lots of advantages, mainly the ability to sit back and let the timer do the work! No dip & dunk! The negs get great agitation and even development. You can easily find 3 1/2 gal. size stuff [made for 8x10 work] but that means lots of chemicals to be mixed and kept up. Since I wanted to do mainly small batches of 4x5 [1 gal.], I chose to make a smaller development tank [I only use gas burst for development] out of a Kodak 5x7 hard rubber tank [easy to drill holes in] and put my piping in the bottom. I've not found any sourcing problems with gas [found everywhere welding gases are sold].

What I did was get the large tank and a valve system which goes on top. Then I bought 100 ft. of small tubing from a woodworking place in New Mexico, along with a smaller step down value used by woodworkers re: air powered clamps. I step down the gas pressure to 25 psi at the main tank, run it through the tubing to my darkroom, and use the step down valve there to step it on down to 15 psi, which is the pressure used at induction into the timer. Works great.

Let me know if I can help further. I just don't understand why other LF photographers don't go this route. It solves so many problems.

-- Alec (alecj@bellsouth.net), February 23, 2001.

Check out E-Bay's darkroom section. There are 2 burst systems for sale. Auction ends 2/25. Price is around $15 at time of this posting.

-- Larry Rudy (ljrgcr@cetlink.net), February 23, 2001.