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#1
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Negative popping
A question: As the negative - in a glassless carrier - absorbs heat from the enlarging lamp, does it pop upwards towards the heat source, or
downward away from the heat source towards the easel? It is given that the emulsion side is facing down towards the easel? Deryck |
#2
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Up, I’m sure. Some carriers have one sheet of glass, normally on top.
Alex Sent from my iPhone using Tapatalk Pro |
#3
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I have found that if a negative has a slight convex surface uppermost it will try to 'pop' away from the curve to make it concave. The 35mm glassless negative carrier on my LPL7700 does not seem to make any difference, I rarely have the problem.
I also have a glassless 6x6 carrier too which did give a problem with 120 negs, so I modified it with a piece of 6x7 anti newton ring lass from a slide mount. I had to modify the hinges as well by inserting a thin washer under the screws of the hinge. so the glass still laid flat. That cured the 'popping' problem and with only one glass surface touching the film, that cut down on the risk of dust on the final print. A bit of a bonus. |
#4
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My negatives always popped up (the shiny side) when I used a Kaiser enlarger.
In my Kaiser, I fitted a piece of IR glass (Kaiser accessory) to reduce the heat transmission into the negative - and it worked - at least partially - popping became much less of an issue. However, in the end I resorted to using glass in the negative carrier - plane glass on the bottom and anti newton ring on the top. Unfortunately, I was plagued with dust on the glass - both sides of both pieces - when I used my Kaiser. Strangely, when I use my DeVere, I still use glass negative carrier (plain glass on the bottom and AN on the top) but the dust is no longer an issue. I have a theory of why the DeVere doesn't have an issue with dust - the entire thing is metal and is grounded to the earth - so there is no where to hold static charge. Almost the entire Kaiser head is plastic and so could hold static charge. It is only a theory - so for those who have better ideas as to why this might be - please share your theories. I also considered wrapping my Kaiser negative carrier in a earthed dissipative mat over night to see if it helped with the problem - but never got round to digging the mat out of my work bag. Martin |
#5
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Theory suggests that a metal head will make no difference as you cannot remove a static charge from an insulator by earthing it (by definition, a charge will not move through an insulator, like film).
But there may be some other action at work: perhaps the frequent touching of the metal head to adjust it, insert the neg etc removes any static build-up from the person handling the film. Dunno - static is tricky stuff and generally, the only way to remove it from an insulator is to add or subtract electrons depending on what charge it has. I think the Zerostat is the only surviving piece of equipment for that now. Alternately, make the surface of the insulator somewhat conductive by spraying it with a semi-conductive coating to provide a path when earthing it, which is how "anti-static" sprays work. You could try zapping the plastic head with a Zerostat and see if that helps. When printing 5x4 negs I use a top carrier of AN glass and a normal metal aperture carrier on the bottom to reduce the number of surfaces to keep clean. |
#6
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Quote:
I'm not saying it couldn't work - but there is no way of knowing whether to spray +ve or -ve ions on to the carrier - and more importantly how much to spray. It could be that for instance I had some -ve static ions on my negative carrier and I sprayed way too many +ve static ions on - so was left with a +ve static charge - which will also attract the dust. Tricky problem to fix. Martin |
#7
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I have an old Zerostat and I know something is happening when I squeeze the trigger, but how do I know if they are negative or positive ions that I am generating?
The original instructions said to slowly squeeze and slowly release the trigger. So does compression give out different ions to the release of the trigger? I know voltage is being generated by the Zerostat as I took a mains neon bulb from an obsolete piece of equipment, connected one wire of the neon bulb to the metal spike in the nozzle of the Zerostat and when the the trigger is squeezed the neon glows. I have never had problems with negatives popping but the maximum size of my negative carrier is for 60 x 60 mm. Out of curiosity I have just made a wooden frame to replace my negative carrier. I drilled a hole in the frame and inserted a thermometer into the space usually occupied by the negative. Room temperature is 27c and after 10 minutes the space for the negative got to 31c. This is on a Durst M605. Glassless masks. I am wondering if anyone having popping problems has thought to measure the temperatures?
__________________
It will all be over by Christmas. |
#8
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Quote:
Squeezing the trigger creates one charge and releasing it produces the opposite. So, I tried squeezing the Zerostat over the negative carrier and then releasing it over something else. I still had the dust clinging to my carrier - so I tried it the other way round, squeezing the trigger somewhere else and releasing it over the carrier - no effect on the dust. I'm not sure I was using it correctly - the box had very few instructions. Any helpful tips gladly received. Martin |
#9
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From my reading, plastics generally get a negative charge. Oddly tho, I find that it does not seem to matter - I slowly press and then slowly release (any clicks means you are too fast) 2 or 3 times from about a foot away. The dust does not go anywhere on its own - you still need to dust it off with a soft brush or blower. Where it scores is that, having done that, it is not attracted back to the film again.
I also zap the whole negative binder sheet before removing the negative. |
#10
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Quote:
Martin |
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