Now that the paper has been prepared, by shrinking and sizing, it is ready to receive layers of colored gum Arabic. The gum Arabic mixture is another personalized part of the gum printing process. You will
notice when you buy premixed gum from B&H Video/Photo or Bostick
& Sullivan that gum is advertised in Baum. Their particular brand is
a 14 Baum. How thick that is I haven't a clue. I mix my own gum. You
thought otherwise? Thirty years ago it was easily found in raw form,
which is, in my humble opinion the best. Now, unless you are interested
in a palate of 100 Kilo bags of raw gum, you will likely be forced to
use the powdered form that seems to be the only choice in the entire
country. It works.
Gum Arabic (Acacia variety) grows from Acacia trees, mostly in far away places unwilling to sell and ship small amounts anymore, without a sizable shipping charge equal to purchasing the palate of 100 Kilo bags. It melts quite nicely in room temperature water, but use distilled water. No free metals needed. If you are sufficiently awesome as to actually have raw gum, cut a square piece of flannel shirt, cotton works too, and tie the measured raw gum up into the cloth and tie string around it, leaving about six inches. Place the measured amount of distilled water in a ball jar and suspend the cloth ball of raw bum in the water just off the bottom of the jar, then put the lid on with the string hanging out so the ball remains suspended when the lid is on. Let it melt overnight.
Gum Arabic (Acacia variety) grows from Acacia trees, mostly in far away places unwilling to sell and ship small amounts anymore, without a sizable shipping charge equal to purchasing the palate of 100 Kilo bags. It melts quite nicely in room temperature water, but use distilled water. No free metals needed. If you are sufficiently awesome as to actually have raw gum, cut a square piece of flannel shirt, cotton works too, and tie the measured raw gum up into the cloth and tie string around it, leaving about six inches. Place the measured amount of distilled water in a ball jar and suspend the cloth ball of raw bum in the water just off the bottom of the jar, then put the lid on with the string hanging out so the ball remains suspended when the lid is on. Let it melt overnight.
The
same procedure is used for the powder form, with exception to all the
steps in the middle. Place the measured amount of gum powder in the
bottom of a ball jar, pour in the measured distilled water and close the
lid. Wait about 24 hours. The gum should be clear if it is a good grade
of Acacia Gum.
The
above use of "measured amount" being, again, there is much latitude in
the gum mixture, but that mixture/thickness or viscosity has to suspend
the pigment enough to keep it from touching the paper, through the
sizing. With the 2 1/2% sizing solution with two coats I use, I
reciprocally use a 50% solution of gum. Thus, my formula is twice as
much water as grams of gum.
The Gum Solution:
I make about 300 ml of solution so as to use it up before it breaks down, and in time it does break down. That comes to;
50% mixture;
300 ml Distilled water
150 g gum Arabic
Also,
important, a preservative is needed to keep the gum from molding, over
time. That preservative is Formalin; which is made from a 10% solution
of [Formaldehyde (37%)]
Use; 5 drops per Oz (30ml) gum solution; for 300 ml = 50 drops {20 drops = 1 ml}
The Sensitizer:
Potassium Dichromate;
Distilled Water 100 ml @ 100 degrees
Potassium Dichromate 13 g
Add dichromate slowly while stirring constantly until completely mixed in. Bottle in dark bottle.
*This mixture represents a saturated solution of potassium dichromate at 13%. Same as silver.
The basic gum mixture for printing is to take about 1 ml of clear gum (eye dropper works well) and place in a small clear plastic cup (1 Oz medical pill cup). Use a small plastic rod or other small rod to pick up a very small amount of watercolor pigment on the tip and mix and stir it into the gum. What you are looking for here is a transparent color that sufficient to leave its mark on the print yet not enough to overtake the other transparent colors that go over it, or a layer it is going over. This is the part that is artistically intuitive. It only takes a few layers of practice before you come to know what a various amounts of pigment are going to do. I use the clear plastic cups so I can hold it up to a light source to look through the color to determine amounts.
When you have the gum color to your liking, pour in an equal amount of the dichromate solution. Much like the Kallitype and Pt/Pd printing mixtures of equal proportion to their sensitizer. For an 5x7 print I used 1 ml of each solution. For an 8x10 print I use double that; 2 ml each solution. I apply mine with a decent quality Sable brush of about 1" to 1 1/2" width for best results.
The next step in understanding gum printing is layering of the colors. How much, which ones and in which order. That is one of the reasons gum printing remains the most versatile, most personally expressive of all the historical processes. There is just so many variables one can alter to achieve so many different outcomes. The variations are endless.
I began printing gums using the standard four color print run. I first began with Magenta, Yellow, Cyan then Black. Here, the black must be watercolor transparent black. This is important, as it being the last layer covers the other three, and if that layer is too thick, it then covers the colors underneath. Too light and there is little affect beyond a bit more shadow density. That is why I have flipped things around now. I now begin with Black, using Black Gouache, which is quite opaque. That wouldn't work on top other colors for obvious reasons. I use the Black Gouache as a base color to achieve dMax, which means I can only print 30% of full print time, to only reach Zone III. Then I float the print to just begin to reduce the black to remain as a deep black up through that tonal range. Then I run the color layers, all transparent, to achieve the depth of color I am after. Sometimes that takes several layers to achieve.
The print below was the last gum print I made thirty years ago. I had not learned about the above method of printing; black first. What I did learn was that a full coating of each layer wasn't necessary, and sometimes counterproductive. I used a 2X eye loop and a few cups of colors, variations on green and yellow/yellow green, and using a very vine brush I added colors to different parts of the tree and foliage. I got creative. I was beginning to intuitively realize the subtler handling of colors and printing times to achieve the enhanced texture and detail achieved with 13 color layers. Now, with digital negatives, this is going to be so much more easily achieved.
Paper: Canson White ~ Sizing; 2 coats 2 1/2%
Gum Mixture ~ 50% ~ 13 color print layers
*Final coat was a thin coat of an 'amber/gold' color mix, thinly brushed on to replicate the late afternoon 'golden glow' effect.
Gum Dichromate Print (from a paper negative) ~ "The Quiet Pond"
1986 ~ 5"x7" ~ Unique
Eugene, Oregon
The Sensitizer:
Potassium Dichromate;
Distilled Water 100 ml @ 100 degrees
Potassium Dichromate 13 g
Add dichromate slowly while stirring constantly until completely mixed in. Bottle in dark bottle.
*This mixture represents a saturated solution of potassium dichromate at 13%. Same as silver.
The basic gum mixture for printing is to take about 1 ml of clear gum (eye dropper works well) and place in a small clear plastic cup (1 Oz medical pill cup). Use a small plastic rod or other small rod to pick up a very small amount of watercolor pigment on the tip and mix and stir it into the gum. What you are looking for here is a transparent color that sufficient to leave its mark on the print yet not enough to overtake the other transparent colors that go over it, or a layer it is going over. This is the part that is artistically intuitive. It only takes a few layers of practice before you come to know what a various amounts of pigment are going to do. I use the clear plastic cups so I can hold it up to a light source to look through the color to determine amounts.
When you have the gum color to your liking, pour in an equal amount of the dichromate solution. Much like the Kallitype and Pt/Pd printing mixtures of equal proportion to their sensitizer. For an 5x7 print I used 1 ml of each solution. For an 8x10 print I use double that; 2 ml each solution. I apply mine with a decent quality Sable brush of about 1" to 1 1/2" width for best results.
The next step in understanding gum printing is layering of the colors. How much, which ones and in which order. That is one of the reasons gum printing remains the most versatile, most personally expressive of all the historical processes. There is just so many variables one can alter to achieve so many different outcomes. The variations are endless.
I began printing gums using the standard four color print run. I first began with Magenta, Yellow, Cyan then Black. Here, the black must be watercolor transparent black. This is important, as it being the last layer covers the other three, and if that layer is too thick, it then covers the colors underneath. Too light and there is little affect beyond a bit more shadow density. That is why I have flipped things around now. I now begin with Black, using Black Gouache, which is quite opaque. That wouldn't work on top other colors for obvious reasons. I use the Black Gouache as a base color to achieve dMax, which means I can only print 30% of full print time, to only reach Zone III. Then I float the print to just begin to reduce the black to remain as a deep black up through that tonal range. Then I run the color layers, all transparent, to achieve the depth of color I am after. Sometimes that takes several layers to achieve.
The print below was the last gum print I made thirty years ago. I had not learned about the above method of printing; black first. What I did learn was that a full coating of each layer wasn't necessary, and sometimes counterproductive. I used a 2X eye loop and a few cups of colors, variations on green and yellow/yellow green, and using a very vine brush I added colors to different parts of the tree and foliage. I got creative. I was beginning to intuitively realize the subtler handling of colors and printing times to achieve the enhanced texture and detail achieved with 13 color layers. Now, with digital negatives, this is going to be so much more easily achieved.
Paper: Canson White ~ Sizing; 2 coats 2 1/2%
Gum Mixture ~ 50% ~ 13 color print layers
*Final coat was a thin coat of an 'amber/gold' color mix, thinly brushed on to replicate the late afternoon 'golden glow' effect.
Gum Dichromate Print (from a paper negative) ~ "The Quiet Pond"
1986 ~ 5"x7" ~ Unique
Eugene, Oregon
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