Tag: gum printing

Time between coating layers

November 20, 2014

breadkenty asked: Hi Tony, I’m very very impressed with your Gum Prints and I wanted to ask you a couple of things. Is it absolutely necessary and important to let each coat to cure for 24 hours before coating another? is it possible to force dry using a blow dryer in between the process? As for the curves, will the curve that you used in your process work with all other kinds of gum prints? I am having some difficulties using the curve calculator to find the correct curves for each CYM-layer. Thanks in advance!

No, it’s not necessary to let each coat cure for 24 hours.  I usually work on three prints at a time and will coat the next layer as soon as the previous layer is dry (typically about 20-30 minutes).  I wouldn’t recommend using a blow dryer as it may cause unwanted effects on the current layer.  I will let each print drip dry from one corner and then will let it hang by clipping two corners with two fans perched in front of a dehumidifier.  This achieves the same purpose as the blow dryer without the potential damage to the layer.  The curve I use for the color separated negatives are the same I use for single negative printing.  Hope this helps.

Tony

Printing the black layer

September 25, 2014

tylerjacobsen asked: Hi Tony, Your gum bichromate prints are beautiful! I’m a photographer and I’m going to start making gum prints. Your blog has been very informative. I do have a question; For the k or black exposure (layer) which neg are you using? In your description of making digital negs (invert, convert to multicolor, split channels), I get 3 separate files, cyan, magenta, and yellow, but no gray channel.

Thanks for the compliment.  For printing black, I use the “C” negative with a short exposure at the very end with WN Lamp Black.  I do three color separations to produce cyan, yellow and magenta negatives. There is no gray negative.  Some people prefer to do four color separations to get cyan, yellow, magenta and a black negative.  All of the test I’ve done for my prints have been with the three color (C,Y and M) negatives.  Hope this helps.  

Tony

Need for sizing

March 17, 2014

rabiephotography asked: hi, thank you for your answer. Just wondering, as most gum processes incorporate gum arabic, potassium dichromate and colours as the basic materials ( I noticed sometimes other additional materials are used) can you please explain the role of gelatine (sizing?) and glyoxal (hardner?) and do you think 4x36W uv units will be enough for exposure (reasonably short)? thanks a lot for your help! •Rabie

Hi Rabie,

Since the Gum Bichromate process can involve coating & developing the paper multiple times (some people do “single coat” gum prints)–it is necessary to pre-shrink the paper before hand.  Doing so removes the sizing of the paper when it was manufactured, therefore the gelatin provides the new sizing and the glyoxal hardens and preserves the sizing.  Check out my post on “Sizing the Paper”.

 https://wordpress.com/block-editor/post/thegumbichromatejournal.com/84

Regarding using the 4x36W uv units for exposure–it would probably work. You may need to adjust your exposure times.  Using step tablets on the negatives are a helpful guide to determining exposure times.

Tony

Alternatives to Glyoxal

March 13, 2014

rabiephotography asked: Hi Tony, always amazed by your work and generosity! thank you very much! I am just starting the process and was wondering what other alternatives to Glyoxal can I use? I can’t seem to find here (NZ). Cheers

Besides formaldehyde which since 1997 has been reported to have links to cancer and has been banned, Glyoxal is the only alternative I know of; and can be found at Photographer’s Formulary:

http://stores.photoformulary.com/search.php?search_query=glyoxal&x=-1253&y=-36

Issues with Glyoxal

February 24, 2014

thefurioustenderness asked: Hello, I have a couple of questions about glyoxal. First, does the diluted glyoxal solution that you use for hardening need to be thrown away after each use, or can it be kept and reused? If it needs to be thrown out, is there a special way to discard it or is it ok to pour down the drain? Second, I have read reports of glyoxal causing yellowing of the paper. Has this been an issue for you? Thank you for your time!

I tend to mix up new glyoxal solution each time I harden although I believe my students have reused the same solution over the course of a few weeks before discarding–I pour the used glyoxal solution down the drain where I teach. There is a neutralizing tank built into our liquid waste system that treats all the chemicals we discard (except for Fixer-we have a separate liquid waste disposal service for the Fixer).  I’ve been using glyoxal for over ten years and have not experienced it yellowing the paper.  Formaldehyde was used when I first learned gum printing in the 80’s but recently the FDA determined it to be a carcinogen and has since banned the use of the chemical.  Hope this helps.  Tony

Flipping the negative

December 31, 2013

nonetodate asked: In looking at your gum prints and process it looks like you don’t flip your digital neg over so that the ink side of the neg is against your pigmented gum coated paper . It appears you expose through the ink side of the digital neg. Why?

No reason, I’ve always printed through the ink side of my negatives.  I find the Epson inks are durable enough to withstand scratching.  

Problems with sizing

June 6, 2013

pmutti-blog asked: I am having problems with all my prints developing a crackled surface, but the paint doesn’t flake off. I am using Rives BFK paper and Gamblin PVA for sizing. Do you know what is causing this problem? When you use gelatin for sizing do you have to use any additional hardening agents? I would appreciate any ideas to solve the problem. Thank you, pmutti

It sounds like a sizing issue which what may be causing the staining you’re having.  After sizing with Knox Gelatin I will harden the gelatin using Glyoxal.  I haven’t used the Gamblin PVA for sizing.  Christopher James combines the Glyoxal with his gelatin to size and harden in one step.  You can check out my post on sizing for more detailed information on my process.  Hope this helps.  Tony

https://wordpress.com/block-editor/post/thegumbichromatejournal.com/84

Exposure Unit

May 28, 2013

pleasekillmenowforiamworthless asked: Did you build your own UV exposure box? I am planning on doing some gum printing at home and your setup looks quite reasonable. Do you know where I can get schematics for building one?

I don’t have schematics for building an exposure unit but I built my exposure unit box by using white Melamine shelves from Home Depot: http://www.homedepot.com/buy/3-4-in-x-15-3-4-in-x-97-in-white-melamine-shelf-1605490.html and four two Strip Fluorescent fixtures 24 inches from Home Depot:http://www.homedepot.com/p/Progress-Lighting-2-Light-24-in-White-Fluorescent-Strip-P7266-30EB/202599765#.UaTmkpVSXZQI use eight Sylvania 20 W 24-inch bulbs (F20T12/350BL/ECO) about 3 inches away from the print.  I ordered the bulbs from http://www.buylighting.com

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I also made an exposure unit for my students at Queens College where I built the box using 2×4 lumber and a plywood top and stapled black cloth on the sides with enough room underneath to be able to place a contact printing frame and make test strips.