Tag: non silver

Gum:Sensitizer ratios

August 4, 2015

windeking asked: I have a few questions about your calibration technique. Did you calibrate for each color? When you did the calibration, how did you determine how long to expose the step wedge? Did you do multiple exposures with the different ratios of gum to sensitizer? In the third set of exposures of your workflow, you say to expose just long enough to achieve tone in step three, but you already have tone up to step eight from set 2. Am I misunderstanding something? Thanks Alan

The exposure times are a result of experiments with different gum:sensitizer ratios with multiple layers.  The exposure time, development and ratio I use are the same for all three colors–with the exception of cyan where I tend to use a slightly shorter exposure time (about 15-30 secs shorter) than the yellow and magenta.  The third set is a short exposure which adds additional color and tone in the shadows for enhanced D-max.  Hope this helps.  Tony

Sensitizer formula

July 6, 2015

irisjeane asked: Hi Tony, I am amazed and inspired by your work! I have recently decided to give gum another try, and I’ve been using a 10% potassium dichromate solution, but I’d like to try ammonium dichromate. Would you suggest using a nearly saturated solution of 29%, or something else? Any advice is greatly appreciated. Thank you in advance!!

Hi.  Thank you for your kind words about my work.  I’ve been using ammonium dichromate for over ten years at a 26% saturated solution.  The formula I use is 13 grams ammonium dichromate to 50ml of distilled water.  Hope this helps.  

Tony

Gum over Van Dyke Brown (part 2)

February 19, 2015

breadkenty asked: Hi Tony, I’m trying to recreate something similar to Edward Steichen’s Gum over Platinum prints for his Camera Work/Vogue Fashion prints. I really like the sharp details that the Platinum print offer with the grain of gum prints over it but I am looking for an alternative to Platinum printing that wont be as expensive. I was thinking Van Dyke but do you have any previous experiences with Gum over Van Dyke or any other processes outside of Cyanotype? If so, what color paint would be best for gum?

breadkenty:

tonygonzalezartist:

I did a lot of Van Dyke before I started doing Gum—but, I haven’t tried Gum over Van Dyke.  Although, I don’t see why it wouldn’t work.  As far as color, in prints of the “Flat Iron Building” and “The Pond, Moonlit” Steichen often used cool colors (i.e. blues, greens etc.) to compliment the brown of the Van Dyke.  That might be a good place to start.  Tony

Thank you tonygonzalezartist, I’ll definitely try the cool color layer. As for actually going about with this project, I’m assuming it would be the same process as you would with single channel gum printing as opposed to having three channels in tri color? In other words I should end up with two different negatives as one is printed with a curve that favors the van dyke and the second one that favors the gum print? My professor recommended that I should gold tone the van dyke to match the hue before applying the gum layer.

Yes, correct-you would make a single negative rather than CMY separated negatives.  If you have a curve you use/like for Van Dyke that’s different from the curve you use for gum printing, then you would make two negatives: one for Van Dyke and one for gum and register them before starting to print.  You can try gold tone for the Van Dyke and see if you prefer with or without.

PDN curve calculator

November 21, 2014

breadkenty asked: Thank you for getting back to me quickly! This helps me so much. For the curves would it be better to find the correct one using PDN’s curve calculator for just one layer and simply apply the same curve to every other layer including the cyan type layer? Or perhaps finding the curve in relation to every other layer?

I haven’t not used the PDN’s curve calculator for my gum prints but it would make sense to find the correct curve for one layer and apply the same curve to all three CMY layers.

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