Vacuum easel for contact printing?

[Rolleiflexible]

I am going down the rabbit-hole of contact-printing Kallitypes. So far, I am printing 8x10s with a traditional contact print frame. Even at 8x10, I am seeing some loss of detail from the negative's content. I would like to print at larger sizes.

I have read that vacuum easels provide a better solution for contact-printing in sizes larger than 8x10. My really stupid question: How does a vacuum easel hold the negative in place on top of the paper? I understand how it holds the paper. Does the easel create enough suction through the coated paper to hold the negative flat against the paper?

If it matters, I am using Hahnemuhle Platinum Rag, a 300gsm paper.

Sanders McNew

 

[MattKing]

A vacuum easel used for this sort of sandwiched application always requires a top glass plate that is larger than your paper and negative. The vacuum sucks the glass and the negative and paper are squeezed flat between the easel and the glass.

 

[Rolleiflexible]

A vacuum easel used for this sort of sandwiched application always requires a top glass plate that is larger than your paper and negative. The vacuum sucks the glass and the negative and paper are squeezed flat between the easel and the glass.

Does this produce a superior image to a simple contact printing frame? I have frames from Century and Eastman -- they are fine examples of their kind, but can I expect better results with a vacuum easel and an overlay of glass?

 

[MattKing]

My experience with vacuum easels is actually in the graphic arts world, so my earlier post was more in the "How Things Work" realm.
The friends I share experiences with - who are currently using contact printing frames for things like kallitypes - are actually using newer frames than yours, and seem to be happy with their results. The few times I've played around with those processes, using their frames, they seemed to work well for me, but I was making smaller prints.
Perhaps a larger and/or newer frame would work better for you?

 

[Rolleiflexible]

My experience with vacuum easels is actually in the graphic arts world, so my earlier post was more in the "How Things Work" realm.
The friends I share experiences with - who are currently using contact printing frames for things like kallitypes - are actually using newer frames than yours, and seem to be happy with their results. The few times I've played around with those processes, using their frames, they seemed to work well for me, but I was making smaller prints.
Perhaps a larger and/or newer frame would work better for you?

I've used an 11x14 Photographers Formulary frame and it was nice but I don't see how it would give a better (or worse) result than the old frames. Flat wood pressed against glass with a steel leaf spring -- assuming the surfaces have no voids, it's hard to see how the age of the frame would make a difference.

 

[MattKing]

I've used an 11x14 Photographers Formulary frame and it was nice but I don't see how it would give a better (or worse) result than the old frames. Flat wood pressed against glass with a steel leaf spring -- assuming the surfaces have no voids, it's hard to see how the age of the frame would make a difference.

I think the frame design has varied over time. In addition, the springs can lose strength and the frames can themselves become less "flat" with time and use.

 

[Oren Grad]

I've used an 11x14 Photographers Formulary frame and it was nice but I don't see how it would give a better (or worse) result than the old frames. Flat wood pressed against glass with a steel leaf spring -- assuming the surfaces have no voids, it's hard to see how the age of the frame would make a difference.

Haven't done alt processes, but I've used several different brands/designs of spring-back printing frames over years of making contact silver prints. As is apparent from patterns of Newton's rings, *none* of them produces entirely even pressure across the negative/paper sandwich, and different frames yield different patterns of unevenness.

 

[gone]

This is a very informative article on that subject, you may have already seen it. They mention that up to 8x10 one should be able to get a good print w/ a regular frame (whatever one's definition of "good" might be), and for anything larger you may need to go the vacuum route.

If it were me I'd try to keep the negative as contrasty as possible, that might solve some of the reduction in sharpness problem.

The Kallitype Process - AlternativePhotography.com

A silver-iron method for the kallitype process, making permanent prints in gold, palladium and platinum metals by Sandy King.

www.alternativephotography.com

 

[Rolleiflexible]

This is a very informative article on that subject, you may have already seen it. They mention that up to 8x10 one should be able to get a good print w/ a regular frame (whatever one's definition of "good" might be), and for anything larger you may need to go the vacuum route.

The article is a great resource — I have relied on it a lot already. In fact, it is the reason why I figured a vacuum easel might give me more acuity in my prints, because it suggests that contact printing frames are not up to the task beyond 8x10. My initial question was how do they work to hold the negative hard against the paper — I gather, now, that I still need to sandwich the negative with a sheet of glass — good to know.

But the bigger question is, does the vacuum easel really make a difference? I know that what the article says. I am wondering what people have experienced when contact-printing kallitypes (or whatever) at larger sizes.

 

[Mick Fagan]

Sanders, long time between drinks.

In my experience, yes there is a difference with a vacuum system as opposed to just compressing between glass.

Similar to Matt, I have experience in the graphic arts field and was familiar with the Nu-Arc vacuum exposure units which were able to vacuum seal well enough to expose A1 paper and A1 printing plates.

After I left the big graphic arts world and ran my own business, I still required a vacuum system for exposing metal backed polymer plates. Metal backed polymer plates I was using were around 4mm thick, 0.7mm of metal and 3.4mm of polymer from memory. Getting these to work well in cheaper smaller units meant finding an exposure unit incorporating a flexible semi-transparent vacuum blanket, that basically shrink wrapped around the plates forming an incredible seal. Resolution of 300 lines per inch was pretty much perfect.

The vacuum bed is basically a grid of pinholes about 20mm apart at each intersection of these gridline marks. My unit had an A3 sized vacuum bed and it worked by rolling the semi transparent (opaque) blind/blanket over everything, reducing wrinkles and anything like that, then turning the vacuum pump on. Within a few seconds everything is pulled down super flat and once an equilibrium is reached, you can expose your plate.

I was using lithographic line and halftone films onto metal backed polymer plates, and in another process directly onto resin coated B&W darkroom paper to make contact prints. My unit was capable of perfect exposure with metal backed polymer plates up to an A4 size, but easily handled A3 sized film to paper exposure.

Prior to getting the vacuum unit with the flexible vacuum blanket, no matter how hard I tried, there was always image crispness fall-off so bad, that anything larger than A4 paper was useless. This was using glass, presumably similar to what you are currently doing.

 

[glbeas]

If all you have is a vacuum easel without glass a sheet of clear mylar laid on top of the paper/negative and extending an inch or so past the edges will do the job. You will need to carefully wipe the air pockets from the center and let the vacuum pull for a bit before exposure to ensure the best contact. Best practice is to cover any remaining holes on the easel to get the highest vacuum.

 

[Rolleiflexible]

If all you have is a vacuum easel without glass a sheet of clear mylar laid on top of the paper/negative and extending an inch or so past the edges will do the job. You will need to carefully wipe the air pockets from the center and let the vacuum pull for a bit before exposure to ensure the best contact. Best practice is to cover any remaining holes on the easel to get the highest vacuum.

Is that a better solution than overlaying with a sheet of glass the same size as the easel? I would think the glass would be better because it should present fewer optical abnormalities, and the weight of the glass would assist in holding the paper and negative together. Or am I missing something?

 

[Rolleiflexible]

Sanders, long time between drinks.

In my experience, yes there is a difference with a vacuum system as opposed to just compressing between glass.

Similar to Matt, I have experience in the graphic arts field and was familiar with the Nu-Arc vacuum exposure units which were able to vacuum seal well enough to expose A1 paper and A1 printing plates.

After I left the big graphic arts world and ran my own business, I still required a vacuum system for exposing metal backed polymer plates. Metal backed polymer plates I was using were around 4mm thick, 0.7mm of metal and 3.4mm of polymer from memory. Getting these to work well in cheaper smaller units meant finding an exposure unit incorporating a flexible semi-transparent vacuum blanket, that basically shrink wrapped around the plates forming an incredible seal. Resolution of 300 lines per inch was pretty much perfect.

The vacuum bed is basically a grid of pinholes about 20mm apart at each intersection of these gridline marks. My unit had an A3 sized vacuum bed and it worked by rolling the semi transparent (opaque) blind/blanket over everything, reducing wrinkles and anything like that, then turning the vacuum pump on. Within a few seconds everything is pulled down super flat and once an equilibrium is reached, you can expose your plate.

I was using lithographic line and halftone films onto metal backed polymer plates, and in another process directly onto resin coated B&W darkroom paper to make contact prints. My unit was capable of perfect exposure with metal backed polymer plates up to an A4 size, but easily handled A3 sized film to paper exposure.

Prior to getting the vacuum unit with the flexible vacuum blanket, no matter how hard I tried, there was always image crispness fall-off so bad, that anything larger than A4 paper was useless. This was using glass, presumably similar to what you are currently doing.

Mick, this is really helpful. (And it has been awhile. I was ... away.) I've seen one of the Nu-Arcs in Clay Harmon's shop -- he used it for polymer plates for awhile, I believe, in making gravures. Do you suppose a vacuum easel overlaid with glass would be a good solution? Or is the mylar an important aspect of the process?

 

[Oren Grad]

How does a vacuum easel hold the negative in place on top of the paper? I understand how it holds the paper. Does the easel create enough suction through the coated paper to hold the negative flat against the paper?

Glass, in this case:

http://www.eepjon.com/VaCFrm.html

 

[glbeas]

Is that a better solution than overlaying with a sheet of glass the same size as the easel? I would think the glass would be better because it should present fewer optical abnormalities, and the weight of the glass would assist in holding the paper and negative together. Or am I missing something?

It would be if you were to seal the edges of the glass to the easel, and this might still cause gaps in the sandwich. The advantage of the plastic overlay is in the contact pressure. In a graphic arts vacuum frame with glass the base is a rubber mat that will conform and allow even pressure. A hard surface vacuum easel wont allow that kind of conformability with another hard surface such as glass.
Also with a vacuum system the weight of the glass is irrelevant. The pressure to make the contact is atmospheric, at full vacuum it would be about 14 lbs per square inch, a figure a glass sheet would come nowhere near supplying.

 

[Nicholas Lindan]

Just to put a vacuum frame's 14 lb / square inch into context it works out to 1 ton / square foot. A vacuum frame, as has been mentioned, evacuates the air between a rubber blanket and a sheet of glass and uses a pump capable of drawing a complete vacuum.

A 'vacuum easel' - box with holes drilled in it - used in conjunction with a vacuum-cleaner style pump won't produce anything like that clamping pressure. Vacuum easels are meant for holding film or paper flat for exposure. The use of an overlay allows them to clamp items together, it won't be ideal but it will be an improvement on a spring-back frame.

Lastly, the clamping force in a spring-back frame is distributed around the perimeter of the frame where the back clamps the glass to the frame. The force in the middle isn't terribly high, but is enough for most purposes.