Negative 'pop'

[Tim Budd]

Hi all,

Recently I have been having a problem with negative pop. My condenser enlarger (De Vere) is causing my negative to buckle smack bang in the middle of my negative (6x4.5), the area size is about the size of a penny. There is the trick of re-focusing once it has 'popped' but wouldn't that leave the area around the buckle out of focus? I could always get some anti-newton glass and fit it to my carrier but what about the dust problem? Cleaning all those surfaces would turn out to be a real pain in the... you know what.

So, is all the hassle with the glass worth it? Or do any of you guys know of any tricks that would work simply?

Tim

Oh, also I am using a 6x6 carrirer so would that leave it susceptible to pop? I might find it very hard to get a 6x4.5 carrier as they don't make my enlarger any more and this particular model is not very common.
:twisted:

 

[Robert]

Can you put heat absorbing glass into your enlarger? Between the bulb and the negative some place..

 

[Ed Sukach]

Can you put heat absorbing glass into your enlarger? Between the bulb and the negative some place..

Agreed. Heat is the problem. Seems like there would have been something like a heat-absorbing filter in there originally - or was there some sort of fan/ ventilation system for the lamp housing?

 

[Tim Budd]

There is no fan or looks like there ever was one but I could put heat absorbing glass there. Would I put it above or below the condensers? Where can I get heat absorbing glass and would it have any effect on the light output?

 

[lee]

Back when I printed with condenser enlargers if I had a neg pop, I would "pre-heat" the neg and let it pop then refocus the neg. That always seemed to fix the issue. I solved the problem permanently by now using a cold light. It gets hot too, but not that hot.

lee\c

 

[Sean]

I just got a 12x12 enlarger that has a big exhaust fan built in, I'm hoping that removes most of the heat...

 

[Robert]

Sean I'm sure that monster you got includes everything including the kitchen sink-))

On my Omega the heat glass slot is between the bulb and the condensors.

Measure the space. If you're lucky it's the same size of one of the common enlargers.

http://www.freestylephoto.biz/sc_prod.php?cat_id=1602&pid=1769

If you're lucky it's the same size.

 

[Sean]

thanks robert

 

[Phil Handforth]

Tim, contact www.odyssey-sales.co.uk the bought Devere in the late 80's and supply refurbs, new and component sales of Devere and other equipment. Their workshop and technical Dept. will be able to help.

 

[MikeK]

Negative pop as everyone has mentioned the heat from the enlarging lamp causing the negative to expand and buckle. The fact you are using a 6x6 carrier is not helping.

I had a similar problem with an old Jobo enlarger I had; and while is was a great enlarger the negative carriers were terrible. I ended up taking an Anti-Newton 6x6 glasss slide ount and carefully took took the glass out and taped it to the top of the carrier and that stopped the problem for me. Downside is keeping the devil dust free!! Upside these slide mounts can handle heat...ever felt the heat from a medium format projector...

Mike

 

[Ole]

I discovered that 35mm negs pop, 6x4.5 negs pop, but LF negs do not! I use glass carrier in my MF enlarger, glassless in the LF. When I put a 6x6 neg in the LF enlarger, it popped... Yet another reason to shoot LF

 

[Robert]

With my enlarger I bet 4x5 is the most likely to pop. When in 4x5 the negative is closest to the bulb. When in 35mm it's pretty far away.

 

[glbeas]

4x5 film usually has quite a bit thicker base than the medium format stuff. No pop there. Then theres the carrier with the tensioning rig made on it.

 

[Boris]

I have LPL 4550 XLG witch has a fan. I print 6x7. The megatives still pop. Wih color I pre-heat them until they pop. Also, doing that gives more consistent color balance since lamp color changes depending on whether enlarger's lamp was pre-heated or not. With B&W this does not always work. Even if I pre-heat, the film may still pop after that or pre-heat time becomes very long. Glass negative holder fixed it all.

 

[Jorge Oliveira]

How long are yor exposures and how open are your lenses for normal enlargement?

It just maybe you have too powerful a lamp.

 

[dr bob]

Jorge has a handle on this problem. The heat that causes the negative to "pop" is almost all infra rays. Conductive heat from the lamp should not be a factor to an great degree (lol). The heat adsorbing glass being discussed absorbs IR, not heat, and they work. Like Jorge says, negative pop may be traced to an overly powerful lamp.

Someone mentioned the heat produced by slide projectors. This heat is conductive and radiated heat, and it is a lot! Kodak used a system of mirrors and heat absorbing glass in the 35mm Carousel projectors and slides still pop. Things are a little less intense in an enlarger. I use a transformer (Variac) on mine to control the luminance and this reduces heat as well. It really extends bulb life too.