nitrogen burst development tank (building your own)

[David Roth]

I am constructing a nitrogen burst development tank for 4x5 negatives. The design I have considered requires drilling tiny holes (#76) in 1/8" or 1/4" acrylic (these are the passage for the flow of nitrogen from the plenum into the bottom of the tank, Gordon Hutchings). I am having difficulty in this department with breaking the drills.

I am looking for a solution to this problem, or possibly an alternate method within the nitrogen burst development realm.

Thanks for any advice. Dave

[Michael Kadillak]

I am on a similar journey. Have you tried to use water to cool your bit?

Planning to use a plastic fabricator to accomplish this objective, but I have heard that these small bits get real hot and melt the acrylic and break when the material cools down and bonds with the bit. Control the temp and you should be fine.

What are you using for your hangers?

Onward!

[Conrad Hoffman]

I machine a lot of acrylic and it can be troublesome. It expands a lot, so even mild heating can bind up tool bits and drills. #76 will typically break if you use it by hand- drill press required. #76 carbide circuit board drills will break if you even look at them the wrong way- stay with HSS (high speed steel). Try adapting a needle to a soldering iron and poke the holes through with that. You may have to put a dimmer or motor speed control on the iron to keep the temperature low.

[Tom Jones]

Acrylic cuts just fine if the drill is designed to drill plastic. Most of your problem is the design of the drill cutting tip. To properly cut acrylic you need the drill to scrape the plastic, not cut in the conventional sense. If the drill tries to cut, as it will with a conventional tip, it tends to dig in. With larger drill sizes this usually results in the plastic breaking. Trying to drill holes with very small drills might result in the breakage you are seeing when they dig in and bind. For the most part, any expansion due to generated heat should be taken care of by the cutting surfaces along the drill shaft.

You can buy special plastic cutting drills, but they aren't always very easy to find locally and a #76 is pretty small. You can, however, easily make your own. Unfortunately, I can't find any decent drawings to help you.

In general, use your grinder to lengthen the point so it looks more like a pencil point than the normal, flatter, drill point. If you do this without concern for grinding the normal rake into the cutting edge, you should find it ending up at about zero rake - just what you want to scrape the plastic without digging in. Then drill slowly, using a drill press so you don't wobble things around and bind it up with side loading. Drill without much pressure to keep the heat and expansion to a minimum and it should work just fine. Good luck!

[Paul Moshay]

Using a light cutting oil like kerosene when drilling will lubricate the bit and keep it from melting the plastic and binding. Also the cutting edges of the drill must be very sharp, using a fine grit wheel and if you know how, make a split point on the drill. Drilling plastic by hand is difficult because the bit wants to dig in, better to use a good drill press to control the feed. I have 30 years owning a precision machine shop and made many parts from all types of plastics. Paul

[Alec Jones]

Wait a minute. This sounds like a design problem. I think of acrilic as a hard plastic. What are you doing - making an acrylic box as the plenum? All this stuff was worked out decades ago. Don't reinvent the wheel.

I'm glad to hear you guys are trying to keep this procedure alive. It is so simple and easy to do, and the results from the even agitation so good, that I'm continually amazed more people don't use it.

Anyway, back to the design. Use flexible plastic pipe. Small, like 1/4" OD. The piping is heated and bent into a winding design which is attached to the bottom of a rack [not the tank]. That way, you can move it from tank to tank. Use a #40 rack for 3 1/2 gal tanks, or smaller rack for smaller tanks. I normally use a small Leedal rack in a 4x5 HR tank to conserve chemistry. I can easily do 5 sheets for one processing. In the large tanks, using 4-ups, you can do 48 sheets per session.

The holes are drilled on the underside of the pipe [relative to the top of the tank] at about 45 deg. from vertical.

Use items made for compressed air tools for the connections. They just slip on. I got mine at Woodworker's Supply of New Mexico. I also used their piping to get from my tank in the garage to my darkroom. That pipe is too thin skinned for the plenum though. Step down the pressure at the tank to 25 psi and then on down to 15 psi going into the timer. There are gauges which incorporate the value into them [again for compressed air, although you're using very low pressures].

You need to be able to disconnect the plenum easily because you'll occasionally get crystalizing of the Nitrogen in the plenum, clogging up the holes. The old timers used Nitrogen humidifiers to avoid this, but I've not seen one in 40 years. Today, you just soak it in alcohol to dissolve the crystals, and get back to processing. It doesn't happen too often, but it does build up.

Hope this helps. Let me know if you have any more questions.

[JanE]

For nitrogen burst, you don't need to drill holes in hard plastic. Use a flexible silicon pipe in which you just pull holes with a needle. I know many big dip and dunk processors in custom labs where this conversion is done to achieve more uniform burst of bubbles.

[Dietrich Floeter]

David, I found this old post and wonder if your design worked and if you had any further input.

[jrshupper]

I have read a little about nitrogen burst systems but have never seen/used one. I understand the argument for using nitrogen,(no oxidation), but in reality, when using 1 shot developers, for around 8-15 mins or so of development.....is that really a problem?

It would seem that using a cheaper source of gas (compressed air in a scuba tank let's say) would be more logical? Correct me if I am wrong.


Thanks John

www.johnshuptrine.com

[CG]

The basic reason for NB agitation has less to do with minimizing oxidation than having fast, efficient, repeatable, automated agitation. Whatever reduced oxidation that may happen is a side benefit.


... I have read a little about nitrogen burst systems but have never seen/used one. I understand the argument for using nitrogen,(no oxidation), but in reality, when using 1 shot developers, for around 8-15 mins or so of development.....is that really a problem? ... www.johnshuptrine.com

[jrshupper]

So...can a system be built using compressed air?

John

[BetterSense]

I'm not sure it would be any cheaper to use high pressure air like a scuba tank. Using regular 100psiish air would work fine with one-shot developers.

My major question is what does the bursting. The name "Nitrogen burst" sounds like the bubbles don't run continuously but in bursts. Do you manually yank open a ball valve and close it real fast or what? Use an electric solenoid valve?

[Michael Kadillak]

I continue to be amazed at the propensity of people in the LF/ULF community to ignore years of proven research when it comes to subjects such as this. Usually the incentive is to cut costs. For over 30 years through today gaseous burst was the state of the art for attaining professional processing results and there are a number of technical reasons that an inert gas was chosen for this task.

I wrote an article a while back in View Camera on this subject and included some technical information from Kodak in it. In this article I disprove the conclusion by Gordon Hutchings in his Book Of Pyro that you need custom tanks and hangers to use N2 burst with pyro developers. Nothing could be further from fact. You can use regular tanks and plenums along with regular Kodak 4A hangers and get absolutely perfect results with pyro developers WITHOUT all of that expensive custom tank and hangers stuff.

If you feel a need to tinker, I would suggest your time would be better spend to tinker with various developers, film and printing papers. Take advantage of the extensive research that has been completed relative to gaseous burst development and utilize it. It will save you considerable time and frustration.

[BetterSense]

I think the bottleneck is that hobbyists, like myself, don't have access to all those "years of research".

[Michael Kadillak]

Send me your direct e-mail address and I will give you all you want to know on the this subject. You can PM me. I regularly support ALL analog shooters in every way that I can.

Best, MK

[iozone]

Michael is right. If you are patient you can find anything you need on ebay. Here is a tank, rack, hangers and plenum on fleabay for $50.00 - Item number: 190463886054
I have seen nitrogen burst timers with solenoid new for about the same price.

Regarding the cost of nitrogen, once you have a tank and regulator the nitrogen itself doesn't cost enough to matter.

This is a GREAT way to work.

I have the same pubs that Michael has (provided by him) I'd also be happy to forward them to anyone who might be interested. Just PM

[Brian K]

Why would someone use nitrogen burst with a one shot developer? Who mixes 3 1/2 gallons of developer for a one shot process? The normal usage of developers with nitro burst is to use replenishable developers. And you don't want to use regular air with that because you will oxidize it faster. The cost of the nitrogen was pretty low and the results were superb.

[jrshupper]

I actually was thinking of building a small tank NB development system that would use much less than 3 gallons--more like 1 liter, for smaller batches. I have access to scuba tanks and could modify a regulator/solenoid combo to use air.

John

[Michael Kadillak]

I actually was thinking of building a small tank NB development system that would use much less than 3 gallons--more like 1 liter, for smaller batches. I have access to scuba tanks and could modify a regulator/solenoid combo to use air.

John

If you have the time and the inclination to do so, by all means go ahead. After about the sixth iteration of producing horrific negatives myself none of which I could point to a semblance of forward progress I was forced to abandon my Thomas Edison tendencies. I realized that my objective was to produce quality prints. The processing of negatives is an intermediary step. My frustration caused me to back up the truck and that is when I found the Kodak technical materials that were the result of years of technical research on the subject of N2 gaseous burst and only then did it all come together.

I sincerely want to encourage you to continue to use sheet film because we are all in this together. My comments above are not in any way pointed or demeaning. I just do not want you to get excessively frustrated. Alistair Inglis knows acrylic like nobody else and he is one of us. He produces what you are looking for. I will also tell you that you can use your compressed air for the stop and fix cycles but it is problematic for sheet film development for the obvious reasons.

Cheers!

[BetterSense]

I'm thinking about doing this for 4x5 in a Kodak hard rubber tank, capacity ~1.75L. Not sure if there's enough space at the top and bottom though, based on what Kodak recommends.

[BetterSense]

I used to work on and build custom paintball equipment, and I have high- and low-pressure regulators, electronics, and CO2 tanks. I suppose C02 would work, other than possibly decreasing the pH of the developer. The only thing I need is a solenoid valve. I have some small ones but I don't think they would pass enough gas.

[John Jarosz]

I suppose C02 would work, other than possibly decreasing the pH of the developer.

Exactly the reason Nitrogen was chosen. Nitrogen is inert. CO2 is not. The pH of a developer is crucial

[BetterSense]

I'm currently using one-shot developer. I guess I could monitor the pH of the developer with ph paper to see if it changes significantly during one development session. Then again, with one shot developer I could probably use compressed air too.

I just rummaged through my electronics and found a 1/8" NPT, 120V solenoid valve, that apparently works. So I'm pretty set now except for the actual gas distributor thing.

[jeroldharter]

The other problem with compressed air is that it contains oxygen. Oxidization of developer, especially dilute one shot developers like pyro can have an adverse effect. That is why nitrogen is used - it won't oxidize the developer.