Contact printing...misinformation?

[ic-racer]

If I were you, I'd try to find some way to close off a dedicated darkroom area and make that as dust free as possible.

Dan

Yes, that has always been a concern, but it is somewhat of a 'clean' workshop for electrical and model building projects. Model and engine building also requires a clean environment. With printing, my greatest prior challenge with dust has been to do 16x20s with 35mm negs, which requires a glass carrier. This IS very tedious but I CAN get it done in this environment.

When projection printing (diffision always) the larger formats and not using the glass carrier, I really DON'T have a dust problem. I guess that is contributing to the frustration.

To quantify it better, when I put a neg in the carrier, sometimes there is NO dust, but most frequently there are a few specs that easily blow off or can be dusted off with on of my brushes. Infrequently there will be a dust spec from drying that is stubborn to remove. I would classify my dust as better-to-average for most darkrooms. I agree that isolating the room could improve that and its on the 'wish list'.

 

[ic-racer]

Within grasp....

I actually stepped away from this project (other than posting here) for a good 48 hours and and now I am motivated to try a few things tonight. Based on all these posts I really feel that the solutions are 'right under my fingertips'

I analyzed the prints I have made so far and my thoughts are that most (if not all) the imperfections in the prints (the ones I made BEFORE I made those 'experimental' prints that I posted) are probably due to the glass and not dust.



The two things I intend to try are:

1) SINGLE sheet of the cleanest glass I have on foam under ENLARGER light
2) A heavy STACK of glass (4 or 5 pieces) on foam under DIFFUSED light

First let me qualify this in that I want to spend maybe one more day working this out before I got to the glass shop and get a nice piece of glass, or before I buy the B&S frame off the internet. Thats why I'm going to do the tests with materials in my possession.

In terms of glass I have about 25 sheets of 'framing' glass. I went through some of them and tried to pick the best sheet. This is all nice glass for framing, some has only been hung once in its lifetime, but, It seems like almost all of them have tiny imperfections in the glass (ones that won't wash off). I think I can find one that has a clear 8x10 opening (the glass is all 11x14 and bigger). In terms of finding the imperfections, they are hard to see on the glass itself, but when the glass is placed on a white piece of paper they show up pretty well as shadows on the paper.

In terms of experiment #2, the glass does not have to be perfect, or even dust free, as the diffuser will take care of that as I already determined. The goal in #2 is to really get some good pressure on the negative so that it will be as sharp as #1 above. I have already shown to myself that #1 above will yield a print that is visually sharper than one of my good 8x10 enlargements from 4x5.

FOAM:
I found a nice piece of foam and used a waste piece of film to see if I could get any residue from the foam to come off on the film and it did not which was comforting to know. The foam was a little dusty so I will try to clean it but I also will try using an upside down piece of RC paper on top of the foam. The thought being that I could actually 'clean' the RC paper, unlike a piece of cardboard or regular paper. Also, I think a piece of plastic would be a dust magnet. If I decide to go this route I will get a nice new piece of foam, of course.

DUSTING:

Maybe this is obvious to you all, but the glass I initially was using was hinged to a heavy metal base with a raised edge so the following was not possible. Anyway, as suggested, the sequence would be to lay the glass down first, dust it, then lay the dusted negative on top. Turn the white lights out and put the paper on the negative, then the foam and what not, and carefully flip it over.

Well I'm pretty excited that I'll have some nice prints tonight and this thread will come to a conclusion.

 

[Alex Hawley]

I ain't ever seen things be this hard. :confused:

 

[lee]

use the 11x14 size glass you don't want to try to line everything up with the 8x10. Framing glass may be too light so you may need to weight the glass down on the edges.

lee\c

 

[richard ide]

Boy!!
If someone ever needed...and I leave the rest to your imagination

 

[JBrunner]

Seriously, though, If you dust your negatives under white light or safelight, let me know. If you do it under white light, what do you do with the clean negative while you are preparing the paper and glass under safelight conditions? ]

If you first clean the glass of the frame with a cleaner as I do, give ample time for drying.

I then dust the glass and negative under white light with an anti static brush. I put the negative in the frame, check it again for dust, switch to safe light, take the paper from the safe, place it in the frame, put the back on, expose and process. I have no problems. Comes out as sharp as a contact print. Occasionally I have to spot one that got by.

 

[DeardorffV8]

In working with contact printing LF negatives I found I got sharper results with 8x10 and larger film sizes by using a vacuum frame. 5x7 and 4x5 were fine with a normal spring back glass contact printing frame.

 

[Anton Lukoszevieze]

contact print frame
negative
paper
light source
timer


image


think

 

[bruce terry]

Good Lord! Why is something so simple and so pure and so well documented by real experts (no, not Ansel) suddenly a math problem?

Dust? Crappy glass? Light? Dark?

Alas, ic-racer, I'm afraid your contact printing dilema requires only logic.

 

[kjsphoto]

Geez, this is not rocket science...

light bulb, glass, paper and you are good to go.

If your prints are soft after you lay glass on top it is your error, learn how to focus better. If dust is an issue that is also your error also, clean you holders, blow out with air, load the film and place in plastic bags, simple done.

These are not math issues, these are user error issues.

Lose the math and get a bulb, glass, paper and good negatives and go print.

You need a good contact frame check out; http://www.pellandphoto.com/

 

[WarEaglemtn]

Einstein and Oppenheimer got together and wrote a treatise on the physics of Contact Printing... it was four pages shorter than this topic.

 

[Kirk Keyes]

Realistically I can get 90mm of column elevation, and I measured an exit pupil of 4mm on a 50mm lens stopped all the way down.

Questions, comments, math errors??

Yes, math errors.

Your enlarge can only go 90 mm? That's about 3 inches. I'm sure you meant 90 cm, or 900 mm. That makes your incorrect 0.022 result become 0.0022.

I would suggest that your estimate for 0.5mm of separation to be too small. You will probably get at least a couple of millimeters separation as both the paper and the film will have some curvature too them.

Also, you haven't accounted for the scattered light that will spread through your negs as them shine down onto the paper from a few millimeters up. You really should use a glass to hold the paper down to minimze this.

 

[richard ide]

"Einstein and Oppenheimer got together and wrote a treatise on the physics of Contact Printing... it was four pages shorter than this topic."

Just wait until this thread advances to the actual processing of said contact prints.

 

[Mike Crawford]

I've been looking at this thread with an increasing sense of incredulity as despite many posters pointing out the simple truth; that contact printing, in principle, is as easy as walking in a straight line, (glass, negative, paper, turn on light), it still appears an impossible quest.

I've only two comments to make which are suggested with the best intentions. As others have said, if the glass is scratched or dirty and leaves visible white marks on the print, obviously buy a new sheet of heavy glass, ideally with bevelled edges or at least with masking tape applied to prevent bleeding fingers in the darkroom. However, if the glass is in top condition and dust keeps appearing, just buy a can of compressed air to blast the offending articles out of your printing vicinity.

My other point, (and I am really starting to realise how boring this post is), is the holy text sought for explaining contacting. OK, Mr Adams kept it brief, because as others have mentioned, there is nothing much to say, (glass, negative, paper, turn on light), but a fascinating resource is the book Darkroom 2, published by Lustrum Press in 1978. The two books in this series simply feature leading American photographers giving an insight into their darkroom practise through folio pages, interviews, and a complete breakdown of the equipment, chemicals and procedures used to shoot, process and print their work. Participants included W. Eugene Smith, Arron Siskind, Ralph Gibson, (founder of Lustrum I think), and most importantly for us here, Cole Weston. Young Cole, son of Edward, has 18 pages to cover contact printing his father's work, and if that's not enough information on the subject, I really don't know what to say. It has wonderful photos of a smiling Cole holding up a roll of toilet paper to illustrate how to clean the glass, and light bulbs for illumination, which puts all ideas of mathematical calculations out of the window. It was that simple all along. But in all seriousness, these books are invaluable resources and give a wonderful insight into how photographers work in the darkroom. Wynn Bullock on tonal print balance and Ralph Gibson on achieving his ideal contrast, (both in the first volume), are marvelous essays. They are long out of print but a quick search on abebooks.com reveall that they can be found quite easily and relatively cheaply.

Happy contacting!
Mike

 

[Ian Leake]

...a fascinating resource is the book Darkroom 2, published by Lustrum Press in 1978. The two books in this series simply feature leading American photographers giving an insight into their darkroom practise through folio pages, interviews, and a complete breakdown of the equipment, chemicals and procedures used to shoot, process and print their work. Participants included W. Eugene Smith, Arron Siskind, Ralph Gibson, (founder of Lustrum I think), and most importantly for us here, Cole Weston. Young Cole, son of Edward, has 18 pages to cover contact printing his father's work, and if that's not enough information on the subject, I really don't know what to say. It has wonderful photos of a smiling Cole holding up a roll of toilet paper to illustrate how to clean the glass, and light bulbs for illumination, which puts all ideas of mathematical calculations out of the window. It was that simple all along...

Thanks for reminding me about this Mike. I shall go away and read that section again

 

[Ray Heath]

g'day all

Mike, i've read those books, they are brilliant and simple

this post, like many others on this site, is just another example of the mis-taken belief that over complicating an issue will make up for lack of experience, confidence and common sense

it don't need to be rocket science

Ray

 

[ic-racer]

Zeroing in...

Update and test results.

So, to update, prior to buying a print frame or formal proof printer box, I have ordered some glass from the glass shop. I decided on 10x12, one-half inch thick.

It is a little frustrating waiting for this sheet of glass from the glass shop, so I thought I would try some things.

Q: How much pressure do you need to hold the neg/paper in contact for a sharp image with A) Collimated light and B) Diffuse light.

A: Depends on the paper. I started with the stiffest paper I had, Forte double weight. Room humidity 55%. This paper still curled up ad the edges with 20! sheets of 11x14 glass pressing on a 9x11 area. The foam used for this test was about 15 Shore (A). I had another 20 or so sheets of glass to put on there but it was getting heavy and cumbersome.

I also tried a base consisting of a one-quarter inch sheet of foam rubber about Shore 40 (much stiffer than the first) and it was A) too stiff and B) not flat enough by manufacture tolerances. I did not try the Shore 40 on top of the Shore 15 foam.

Ilford double weight fiber base was held flat under the 20 sheets of glass and the Ilford RC paper also was also held flat.

With this setup I was unable to test collimated light (the light was diffused by all the glass).

I did try a single clear thin piece of framing with weights or pressure on the edges, however, the glass bends and is not in good contact in the center. So, again, I was unable to do this test with collimated light until the thick glass comes in.

So, to recapitulate:

It is impractical to obtain good control with VC paper with a light source consisting of "any light bulb"

Overlay glass needs to be 1) free from bubbles or scratches if one intends to use collimated light. Minimum thickness for a 'gravity pressure' system has not been stated and needs to be determined (for my own work that is).
ANY small imperfection or dust on the glass or negative with show up with precision when using a collimated source.

A diffuse light source removes the shadows from dust and all imperfections in the glass. Dust that gets caught between the neg. and paper still shows up.

If the paper and negative are in close enough contact, both collimated and diffuse light sources produce identically sharp prints.

For a contact printing system to be useful in making fine prints (in my darkroom), there must be provisions for the frequent placement of test strips or paper in the system, without compromising the cleanliness of the negative. Also, when using strips of paper, the negative needs to be in-contact with a clean surface.

For a contact printing system to be useful in making fine prints silver prints on VC paper it has to be designed in such a way that the negative can be loaded on the glass in the light (to facilitate dust removal). The may require inversion of the system or adhesive to attach the negative to the glass.

 

[Alex Hawley]

Minimum thickness for a 'gravity pressure' system has not been stated and needs to be determined (for my own work that is).
ANY small imperfection or dust on the glass or negative with show up with precision when using a collimated source.

Now you're getting somewhere. You need to determine pressures with the various thicknesses of papers, film, as well as the printing frame latching system. If you're going to optimize tis system, these numbers need to be quantified. There also need to be a quantificaiton of the pressure variation across the negative/paper laminae on both the X and Y axis. Then we need to know how this pressure varies with the latch spring material be it spring steel, stainless steel or brass. Please include the material grades, heat treatment, typical yield and ultimate strengths. I would also like to see how you determined the spring constants for the various components if you use a mass-spring modeling system.

As for the light source, glass imperfections, and dust particles, the realationship needs to be established as to minimum sizes of particles and imperfections that can be tolerated with respect to light source distance from the exposure plane.

Please include all calculations and assumptions to that we may follow the methodology for your conclusions. I would like to be able to validate this work.

 

[Mike Crawford]

Good lord Alex, I think you are on to something here.The paper to film thickness variation was obviously the key to any significant variation that the printing frame latching system might possibly yield. We were damn fools not to see it before. However is the notion of the X and Y axis still valid when we still have no definite proof that the minimum size and tolerance ratio of glass imperfection has still not been at least 97% validated.

The answer awaits.

Count me out of this thread. I enjoy printing too much to look any more!
Cheers and good luck,
Mike

 

[Alex Hawley]

However is the notion of the X and Y axis still valid when we still have no definite proof that the minimum size and tolerance ratio of glass imperfection has still not been at least 97% validated.

Mike, the pressure variation in both the x and y directions is important so that a pressure compensating mechanism can be constructed. One of the major problems with traditional latches is that the pressure tends to concentrate where the latch is attached or makes contact with the pressure back. It then deceases radially until it is met by the similar pressure gradient from an adjacent latch.

This needs to be known before the defect sizes are determined since the minimum allowable defect size will vary inversely with the pressure gradient. With current designs, different size particles and glass defects have varying degrees of effect on the prints.

 

[Mike Crawford]

I'm very glad to have this invaluable update. I think I will sleep well tonight. Now I really am out of here!
ZZZZZZZZZZZZZZZZZZZZZZZZZ

 

[CBG]

PLEASE don't buy an 8x10 enlarger. APUG doesn't have enough file space on their servers to help you accomplish using one. If you can't contact print GIVE UP! My wife and I have taught kindergarteners how to contact print and with excellent results. I can't believe this discussion has gone on for 5 pages!

Walker

Like many others, another technophile / techno-victim is thinking and analysing waaaay too much. I would urge the OP take a class somewhere and see the process done.

Some things really are simple at their essence,

C

 

[Ray Heath]

hey ic

i think you must have made a few typos;

20 sheets of glass would just be silly

giving foam specific names/serial numbers would be a little too anal, foam is soft and squishy, another named/rated/ numbered foam would be amh, i don't know, soft and squishy

the fact that you posted all this info leads me to suspect you didn't see the previous posts, is your computer/screen/web browser ok cause you couldn't have read any of those posts

 

[richard ide]

I am biting my tongue as I ask: Do you work for government?
I have made well over 50,000 contact prints ranging in size from 4 x 5 up to 60 x 144 and never once has it ever been 95% confusing. I have even used a piece of glass, cardboard and paper clips to make contact prints. Not the best but it works. You are making this 20X more complicated than it needs to be.

 

[Alex Hawley]

Actually, this would best be done using a matrix of strain gages mounted in all three planes (x, y, z) at each corner of the frame, in the middle of each frame member, then a matrix at several points on the back and on the glass sheet. That would allow actual deflections to be be measured. The forces applied and bending moments could be calculated from those direct measurements. Of course that depends on the properties of the frame's materials, so then we get into the type of woods being used, wood grain orientations, saw orientation, and of course, moisture content at time of testing.

Once the first test is complete, then we can vary the types of woods and joint constructions used in the frame, along with glass types and thicknesses. I'm excited!