Slowing down Unicolor motor to decrease agitation

There has been discussion on this and the film forum about the

problems of continuous agitation of black and white film during

development. Some of us are adapting old Unicolor drums and motorized

bases for sheet film development. If the rapid agitation is a

problem with this type of system, why can't you attach a rheostat to

the line and slow down the drum to decrease agitation? Would that

burn out the motor?

Steve, the problem is not related to the speed of rotation. It concerns the principal of using continuous agitation, resulting from the constant rotation of the drum. According to Anchell and Troop, edge effects can be obtained with most film developers if the film is allowed to stand motionless in the developing solution for a period of time. The developer exhausts itself in the dense areas. Then, gentle, deliberate agitation brings fresh developer into play, again. They recommend ten seconds of gentle agitation during each sixty seconds of development time. I am in the process of submitting an illustrated article to Tuan's large format website (largeformatphotography.info) that describes an alternative way to develope 4X5 sheet film, utilizing a simple dip and dunk developing set-up to accomplish this method of intermittent agitation.

If its a synchronous motor it will not work, you must vary the frequency., but if it's motor with brushes you can vary the speed with a light dimmer, like a variable speed drill. You must open a see what kind of motor it has inside, if it looks like an old record player motor (50s and 60s)it'sycnhronous.

Jacques

Don't do it ! AC motor speed is based on line frequency (60hz) not line voltage. A rheostat knocks down line voltage not frequency. The motor will get really hot and eventually burn out.

I've been using a Beseler drum on a Beseler motorized base to develop TriX sheet film in HC110 B for about 8 months now. It works fine. I don't see any evidence of non uniform developement at all. I use 6 - 8 oz of solution to develop up to four sheets at a time.

If too rapid agitation is a problem, one could always pick up one of the old 16X20 drums and cut them down to the size needed for 4X5 or 8X10 sheet film. The 16X20 drums have a much larger circumfrance and consequently slower effective rotation.

A slightly different question: I just bought a Jobo expert drum, thinking I would use it with the Unicolor base. I've noticed though that the diameter of the expert drum is so large that it does not seem to make even a full revolution on the Unicolor base before it reverses direction and heads back the other way. Doesn't this mean that some of the film chambers won't receive solution, hence making it useless for processing without some kind of modification?

All AC motors must be regulated in speed using a duty-cycle adjustable circuit, such as one using a FET type power transistor and adjustable resistor on the gate circuit to alter the duty cycle.

 

Merely using a light dimmer switch will decrease the voltage to each winding, which causes the current demand to increase, thus motor burnout.

 

Other than electrically controlling the motor speed, how about mechanically altering the drive ratio from the motor to the drum. Different sized pulley/idler wheel?

I don't think this is a real problem!

If continuous agitation is bad why does John Sexton use it? He's the first to come to mind but there are others who have success with continuous agitation.

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And I suggest you test this for yourself rather than acting on things you read here or anywhere else. Different developers and films probably do behave differently in differnet agitation methods. My continuous agitation results agree very much with those of John Hicks who has posted at:

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href=http://unblinkingeye.com/Articles/Rotary/rotary.html>http://unblinkingeye.com/Articles/Rotary/rotary.html</a>

In which he shows curve comparisons that support this statement:

" I also found that contrary to conventional wisdom there were no significant differences in curve shape resulting from using continuous rotary agitation vs. intermittent agitation."<br>

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I've used the 1500 series Jobo tanks and the 2500 series tanks on a Unicolor motor base with good results. If you test your methods and techniques and tune them accordingly you can get the result you want many different ways. I also use the same tanks for inversion. By varying the time I can get closely matching results either way. Film speed might change, curve shapes seem to stay very much the same. Twelve sheets in a 2500 drum on a motor base is a very convenient and consistent way to process your film. Obviously you miss the chance to do plus or minus development within that batch of film. Thats the -only- downside I can think of.

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There are probably about as many film development methods as there are photographers. Lots of them good.

Henry, nobody said that continuous agitation is BAD. Most of the people who are using PMK developer (or other Pyro formulas) are doing so for the EDGE EFFECTS that they can obtain with those types of developers. Anchell and Troop claim that similar EDGE EFFECTS can be obtained with most film developers, if the correct agitation pattern is used. Continuous agitation using trays or one of the rotary development methods does not seem to produce those kinds of effects. Of course, rotary development produces smooth, even development, without streaking.However, it does not produce the type of EDGE EFFECTS that some photographers are trying to obtain when they process their negatives.

Eugene,

 

I'd really love to see some of these "edge effects" you are talking

about. Maybe the same neg processed both ways for

comparison. Have any suggestions?

 

Thanks

Jon, I'm sure that you realize that it would be impossible to process the exact same negative using two different methods of agitation. Two shots of the same subject, side-by-side, processed with the two methods, would probably work. I don't own a rotary processing system. Perhaps someone who owns one could develope the other negative, using the identical developer, as a comparison. I have been playing with a dip-and-dunk system based on a set of three HP Combi-Plan tanks, using slow intermittent agitation. So far, it seems to be working very well. Look for my article on Tuan's LF website in the near future. Meanwhile, read about edge effects in "The Book of Pyro", by Gordon Hutchings. Or, "The Film Developing Cookbook", by Anchell and Troop. It's an interesting concept.

Eugene, Steve (the original poster) didn't ask about PMK he said "problems of continuous agitation of black and white film during development" My position is that it is not always a problem. It might be with some developers as you apparently have found out. And you may know Steve and know that he's working with PMK - I don't know that, he didn't post it.

 

I got your EDGE EFFECTS comment (don't shout ; >), but I don't see where Steve mentioned edge effects either. And I have a well-read and dog-eared copy of Anchell & Troup as well. And I say that continuous agitation is not necessarily a problem! Sometimes its a good technique.

 

If anyone is using a Jobo 2500 tank system for 4X5 and wants to try minimum agitation, do this: fill a 2 reel 2500 Jobo tank with enough developer to cover the film, (1.25 liters for 1 reel of 6 sheets so it can be quite dilute if you want) then drop the film in and roll it gently by hand for 30 seconds then stand it up. Later, lay it on its side and roll -slowly- it one revolution, then stand it up. Do that once every (you pick the interval) until you find a development, agitation, time, technique that gives you what you want in your negatives. What I found when I did this was that the Uniroller gave the same result with just a time adjustment. Now thats with Xtol or D23 or a glycin/metol developer of my own mixing. As to PMK I can't say, but if it benefits from minimal agitation this might be worth a try. Your idea of small dip & dunk tanks sounds great and I bet its a real good way to control agitation. I personally like to do it with the lights on! But trays in the dark is good too. Whatever floats your boat.

 

Anyway, neither of us answered the question about how to make the drum turn slower!

I will say I have thought more than once about a motor roller base that was nicely sealed against moisture and electrical shock and fully adjustable for speed, interval of reversing direction, and different sized tanks.

Eugene,

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>I'm sure that you realize that it would be impossible to process

the exact same negative using two different methods of agitation.

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Sorry Eugene, I thought you would understand that I meant the

same image on <i>two</i> pieces of film... so much for clarity...

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> Perhaps someone who owns one could develope the other

negative, using the identical developer, as a comparison.

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I'm game, my Uniroller should arrive next week. Do you want to

shoot the negs or shall I?

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>Look for my article on Tuan's LF website in the near future.

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I'll keep an eye out for it.

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>Meanwhile, read about edge effects in "The Book of Pyro", by

Gordon Hutchings. Or, "The Film Developing Cookbook", by

Anchell and Troop. It's an interesting concept.

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I've perused Anchell's books several times. Guess I'll have to

break down and buy them...

 

Thanks

I thank everybody for their responses: the ones about burning out the motor and the ones that discussed "edge effects" issue.

 

I normally use d-76 or d-23 and have been thinking about trying PMK or some type of staining developer as well. I used to use stainless film holders and the dip method in deep tanks, but found I was getting some uneven development in the sky regions. I later switched to Ansel Adams' tray development method and no longer had uneven development. But, it has been a long time since I had a darkroom in the house, so the Unicolor drum sounded great for daylight development that would be even.

 

The debate here about the pros and cons of continuous agitation leave me to test this for myself, which I would have done anyway.

I agree with Eugene:

 

>There are probably about as many film development methods as there are photographers. Lots of them good.

 

I am suspicious any time someone says: "you have to do it this way."

 

If I may add some of my own opinion here:

 

Contrary to what some LFers may think, photography is an art form, which like all other art forms is an interpretation of what the artist envisions. Photography is not an accurate representation of reality, no matter how sharp the lens, how large the negative or accurate the colors/tones. Its a two dimensional rectangle with gradations of tones and colors, the range of which is choosen by the artist to make the finished product that was originally envisioned. For some people this may mean nice sharp edges, for others smooth tones, or large chunky grain, or sepia tones, or infrared interpretations, etc. There cannot be a right or wrong here.

 

There, I got that off my chest. Please forgive me for getting on a soapbox.

 

Thank you all for your thoughtful responses.