Color Balance For Gum Prints

Bruce · Oct 26, 2010

All

How do you achieve color balance for gum prints?

I am trying to do Tri-Color gum and can't seem to get a decent print. Most are to muddy in color after my 3 coatings.

I assume I just have to work with the individual pigment strenghts as well as exposure time to get a balance I like.

What are your thoughts?

Thanks

Bruce

donbga · Oct 26, 2010

BruceRC said:
All

What are your thoughts?

Tell us more about how you are making your prints.

Don

R Shaffer · Oct 26, 2010

For me it was a lot of trial and error along with many test strips of various pigment concentrations.

I would agree with Don that more info on how your making them now would help and maybe an example image.

Bruce · Oct 26, 2010

Don Bryant said:
Tell us more about how you are making your prints.

Don

Don - I just knew you would ask for data so here it is

Gum - Daniel Smith

Paper - Fabriano Artisco Extra White Sized in water and then coated with PVA at 1 part PVA to two parts water

Pigments M Graham
Blue Phthalocyanine Blue at 15ml tube pigment to 485 ml gum

Magenta Quinacridone Rose 15ml tube pigment to 285 ml gum

Yellow Azo Yellow 15 ml tube pigment to 485 ml gum

(Note: These were same pigment/gum ratios used at a gum workshop)

Concentrations used for small print 6 x 9
teaspoon pigment/gum
teaspoon ammonium dichromate

Exposure time for each of the 3 layers - 7 minutes for first print looked to dark.
4 minutes for second print. Better but still needs work

Thanks for the help.

Bruce

donbga · Oct 26, 2010

BruceRC said:
Don - I just knew you would ask for data so here it is

Gum - Daniel Smith

Paper - Fabriano Artisco Extra White Sized in water and then coated with PVA at 1 part PVA to two parts water

Pigments M Graham
Blue Phthalocyanine Blue at 15ml tube pigment to 485 ml gum

Magenta Quinacridone Rose 15ml tube pigment to 285 ml gum

Yellow Azo Yellow 15 ml tube pigment to 485 ml gum

(Note: These were same pigment/gum ratios used at a gum workshop)

Concentrations used for small print 6 x 9
teaspoon pigment/gum
teaspoon ammonium dichromate

Exposure time for each of the 3 layers - 7 minutes for first print looked to dark.
4 minutes for second print. Better but still needs work

Thanks for the help.

Bruce

I assume since you are posting here on HybridPhoto.com you are using digital negatives of CMY or CMYK files created in Photoshop.

What is your methodology for creating your negatives?

Whose workshop did you take?

Don

Bruce · Oct 26, 2010

Don

I took a wonderful workshop from Chris Anderson at the Photo Formulary in Montana. Highly recommend her workshops- super person and great instructor.

I am using seperation negatives made in Photoshop using RGB and splitting the channels. Chris used this technique at the workshop.

Negatives printed on either Inkpress film or Pictorico OHP.

Bruce

donbga · Oct 26, 2010

BruceRC said:
Don

I took a wonderful workshop from Chris Anderson at the Photo Formulary in Montana. Highly recommend her workshops- super person and great instructor.

I am using seperation negatives made in Photoshop using RGB and splitting the channels. Chris used this technique at the workshop.

Negatives printed on either Inkpress film or Pictorico OHP.

Bruce

Are you creating a correction curve for each pigment?

What is the order of pigment printing?

Is your ammonium dichromate saturated?

Don

PVia · Oct 27, 2010

All of the above, Bruce...

There are so many variables.

How were the prints you made at the workshop? Did they turn out better than what you're experiencing now?

Davec101 · Oct 27, 2010

Don Bryant said:
Is your ammonium dichromate saturated?

Don

Hi Don

I am using Potassium Dichromate at the moment, is there a big difference between the two, what do you mean by saturated? thanks

donbga · Oct 27, 2010

Davec said:
Hi Don

I am using Potassium Dichromate at the moment, is there a big difference between the two, what do you mean by saturated? thanks

Hello Dave,

The very brief and simple answer is compared to potassium dichromate used in a saturated state, saturated ammonium dichromate will print faster (increased UV sensitivity) and produce a longer scale (more steps in a step tablet print). Also the ratio of dichromate to pigment will affect printing speed.

So how do we make a saturated solution of PD or AD (sodium dichromate isn't normally used since it is very deliquescent)? Well I take a specific volume of distilled water (usually a half liter) and add dichromate until it refuses to dissolve. For PD this will produce roughly a 13% solution and for AD this will be about a 27% solution. Thereafter I always make sure that my dichromate bottle has undissolved crystals on the bottom of the bottle. That way I always know EASILY what my dichromate concentration is before I use it.

I prefer to use AD because it prints faster and gives me a longer scale. Some gum printers prefer PD.

Does that help?

Don

Davec101 · Oct 27, 2010

Don Bryant said:
Hello Dave,

The very brief and simple answer is compared to potassium dichromate used in a saturated state, saturated ammonium dichromate will print faster (increased UV sensitivity) and produce a longer scale (more steps in a step tablet print). Also the ratio of dichromate to pigment will affect printing speed.

So how do we make a saturated solution of PD or AD (sodium dichromate isn't normally used since it is very deliquescent)? Well I take a specific volume of distilled water (usually a half liter) and add dichromate until it refuses to dissolve. For PD this will produce roughly a 13% solution and for AD this will be about a 27% solution. Thereafter I always make sure that my dichromate bottle has undissolved crystals on the bottom of the bottle. That way I always know EASILY what my dichromate concentration is before I use it.

I prefer to use AD because it prints faster and gives me a longer scale. Some gum printers prefer PD.

Does that help?

Don

Yes thanks, at the moment i am getting my p.dichromate pre-made in liquid form from bostick and sullivan so i may have to start making my own, i do hate making it though as its nasty stuff.

Bruce · Oct 27, 2010

Don/PVia

I am using the same negatives that we made at the workshop. We had a correction curve for each negative.

The pigment printing order is the same -- Thalo Blue, Yellow and then Magenta.

I think my dichromate is saturated- I'll have to go back and recall how I made it.

Prints at workshop were better than I am presently getting. I think I just have to play around with exposure times as well as pigment/gum concentrations.

Bruce

donbga · Oct 27, 2010

BruceRC said:
Don/PVia

I am using the same negatives that we made at the workshop. We had a correction curve for each negative.

The pigment printing order is the same -- Thalo Blue, Yellow and then Magenta.

I think my dichromate is saturated- I'll have to go back and recall how I made it.

Prints at workshop were better than I am presently getting. I think I just have to play around with exposure times as well as pigment/gum concentrations.

Bruce

So are you now using a different light source? I assume that you are unless you palmed the one from the Formulary. That will make a difference in your negative calibration.

How did Chris instruct you to determine your minimum printing time?

Can you scan some prints and show us a before and after? At the workshop and now at home.

Don

Bruce · Oct 27, 2010

Don

Yes I am using a different light source (made my own UV box) thus my exposure times will be different than at the Photo Formulary. I printed some step wedges to help guide me in determining what might be a good starting point for exposure. I realize that my first prints may be overexposed. Thus t I am cutting the exposure time down to less time

Chris had already determined exposure times at the workshop based on step wedge print test and other test prints she had at the workshop.

Not sure if my scanner is working properly so it may not be possible to send photos at this time.

Over the next few weeks I'll keep experimenting.

Bruce

Katharine Thayer · Oct 27, 2010

Bruce,
Is that plain azo (PY151) or nickel azo (PY 150)? Makes a big difference to my answer.

More later,
Katharine

Bruce · Oct 28, 2010

Katharine Thayer said:
Bruce,
Is that plain azo (PY151) or nickel azo (PY 150)? Makes a big difference to my answer.

More later,
Katharine

Hi Katharine

I was supposed to order PV 150 Nickel Azo Yellow but I somehow ordered PY 151 Azo Yellow. I know it will make a difference in the final color balance.

Bruce

Katharine Thayer · Oct 28, 2010

Ah, I suspected as much; that could well account for your problem right there. In my experience, problems with color balance, and especially with "muddy" color, are almost always a result of unfortunate pigment combinations. PY 151 is an extremely high-value (pale) yellow; I would never choose it for tricolor work. Good luck,

Katharine

Katharine Thayer · Oct 29, 2010

Bruce, I have a page on tricolor printing here, FWIW:

http://www.pacifier.com/~kthayer/html/tricolor.html

Bruce · Oct 31, 2010

Katharine Thayer said:
Bruce, I have a page on tricolor printing here, FWIW:

http://www.pacifier.com/~kthayer/html/tricolor.html

Katharine

Thanks for reminding me of this info.

Bruce

Color Balance For Gum Prints

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