Pin Registration Board for Three Color Gum Printing

Here is a pin registration board I created today for making large color gum prints. It consists of white marker board from Home Depot, a strip of aluminum epoxied to the lower edge of the board to act as a base guide, and three registration pins taped into place on the left. Note: this is the same piece of board I showed in a post from 2016 when I was working in the gumoil process just re-purposed for color printing. It was a plain, flat board back then used for stretching full sized watercolor papers and measures 24″ x 32″. I can tape the pins anywhere near or far apart depending on the size of the print.


The next image shows what it will look like with a full size sheet (22″ x 30″) of Fabriano Artistico Soft Press. The blue mat board is only there to simulate a thin sheet of 24″ x 36″ aluminum to which the paper will be temporarily bonded using Fusion 4000 dry mount film and a heat press. The aluminum sheet will rest on the 3/4″ x 1/8″ thick aluminum bar at the bottom, and will bump up to the registration pins on the left for consistent placement.


Again, having neither the aluminum sheet nor large separation negatives at the moment, I’ve tried to simulate an added piece of extension film with the registration holes punched into it and taped to the negative.


Here are the registration pins. I ordered two different heights, but all have 9/32″ pins. I am not sure which height I will need, but I suspect the shorter ones will suffice.


For punching the holes in the negative extension sheets, I found a 9/32″ hole punch this morning at Staples for $15.


I removed the center punch to give a larger spread between holes. My plan is to punch two holes; one in the center and the other near the bottom. Then I will slide the outer hole punch up to align with the existing center hole and punch a third hole at the top end of the negative extension sheets. This will give me a 17″ span between top and bottom holes plus one in the center.

holepunch-1Before I can use the punch, I will have to cut a slot in the sides at both ends to allow for the wider film. I’ve marked where the metal will be removed.

holepunch_mod-1 The advantage of this configuration is that I don’t need an expensive commercial registration punch AND will not need to punch holes in either the paper or the aluminum. In addition the paper will not stretch or shrink while printing multiple layers while mounted to the metal sheet. One down side will be having to align and tape down the pins for each size print. How well does it work? I will find out in the coming weeks as I complete my initial calibrations for gum printing.


Waxing prints and Mixing Gum: Could a Wednesday evening be more fun?

Today I decided to add a layer of Dorlan’s Art Wax to my gum bichromate prints. The wax adds a measurable degree of clarity and depth to the colors which may not show here, but I’ll post it anyway:

gum_prints_waxedIn addition, I mixed up my first batch of gum arabic (gum acacia). I tried to duplicate a formula used by Hans de Bruijn in the Netherlands. I got carried away with adding the distilled water and now the solution is a bit thinner than it should be. The Specific Gravity should measure 1.107 or 14 degrees Baume. Instead it calculates to 13 degrees. It’s now on top of the refrigerator where I’ll let some of the water evaporate overnight.



New UV Printer and Vacuum Frame

I Finally completed my new UV lights and vacuum frame. It will accommodate a full sheet of watercolor paper with room to spare. It uses 24: F30T8 BL bulbs and six electronic ballasts for the light source. The black skirt is made of felt and blocks stray UV. The bulbs are suspended just 2″ above the vacuum table.

uv_printerHere’s a peek at the 24 black light bulbs. The end sockets are mounted to a sheet of 3/4″ maple plywood with a layer of galvanized steel in-between as a ground plane for the bulbs. Below the bulbs you can see three computer fans used to cool the bulbs during use.

blacklight_bulbsAn electric hour meter will keep track of bulb usage.

hour_meterAnd here’s the vacuum table showing the Kreene film partially unrolled. The usable (black) surface measures 27″ x 38″ with an overall size of 35″ x 44″ of maple plywood. The vacuum pump runs on 12 volts and was re-purposed from an old automobile windshield repair kit. It is powered by a 33Ah battery and a smart trickle charger. At the front of the table is a bleeder valve to control the amount of vacuum for various processes. So far I have seen the pump pull a maximum 16 inches of vacuum on this table. The black textured surface was purchased from Lowes hardware and is contact glued to the plywood. Surrounding that is 3/4″ Velcro (self-adhesive, hook side). A hole is drilled near the upper right and lower left corners of the Velcro and brass hose couplers are epoxied into the holes on the bottom of the table. Plastic tubing of 1/4″ i.d. is fitted onto the brass pieces and connected to a “tee.” Then a single tube runs to the vacuum pump.


F30T8BL bulbs


Kreene vinyl film

Textured black rubber mat Available at Lowes stores in the kitchen shelving area.

Hour Meter: search for “110v hour meter”

First oil print using a dedicated negative

After some testing for optimal color, exposure time, etc. Here is the first print made with a dedicated negative. Bristlecone pine roots.

20160501-roots-oilprintThe neg color was 130-100-60 on the HSB scale.

20160501-roots-oilprint-negAnd here is a screen shot of the Photoshop adjustment curve used to linearize the mid-tones.

oilprint-curveThere is a lot of work still to be done in fine tuning all of the techniques.

More test prints and a drying frame

Today I tried printing using another batch of old negatives. I used the last papers poured a week ago. These prints were all made with the 4″ foam roller. While I like the photo-realism of the roller, I will soon be trying brushes to apply the oil-based ink. First, here are the three negatives I used:

digi-neg-trioAnd here are the three oil prints done today:

Chess table in Chatuchak Park, Bangkok, Thailand.

chess_oilThe Manger (from Gertrude Kasebier negative – National Archives)

manger_oilMJ -the original was shot with a point-and-shoot camera under harsh lighting, but this print accentuated the high contrast.mj_oilHere’s an attempt at drying a print with a reverse-curl frame. I’m hoping that as the gelatin shrinks, it will pull on the clamps and begin to straighten the thin 11×14 acrylic sheet the image is resting on and not tear away at the edges.



Fresh batch of gelatin

Yesterday, 4/15/16, I mixed up 1-1/2 liters of gelatin in preparation for pouring a dozen sheets of future oil print paper. For my own future reference, here’s the recipe:

120g gelatin (for an 8% mix)

50mL isopropyl alcohol

7.5mL of a 1% chrome alum mix

1.5mL glycerin

Distilled water to make 1.5 liters

Here are some shots of the day:

Three leveled pouring stations made of plywood, plate glass, and galvanized sheet metal.


Freshly poured clear gelatin with 0.035″ magnetic vinyl strips to act as a dam. I use 80mL per sheet and smooth the liquid with a heated stainless steel rod. Each paper is 11″ x 14″

fresh_pourSheets are hung to dry for two days.



First Test prints

Finally had a chance to ink up a couple of test prints. The first was overexposed but shows some good relief detail in the Bristlecone pine forest. I used an old digital negative made for platinum/palladium.

tree_detailNext test was an abandoned cabin near Fairplay, Colorado. again, this was made with a digital neg made for Pt/Pd.

cabin_first_printHere’s a closeup of the cabin with a ruler to give scale.

cabin_detailThe inking was primarily done with a 4-inch foam roller. I then tried modifying local contrast with a 1-inch bromoil brush. I used Graphic Chemical 1496 Black Lithographic ink. The matrix soaked in 70-degree water for one hour before inking. The paper was made a week earlier with an 8% gelatin mix and poured using 0.035″ magnetic strips as a dam. The solution is leveled with a heated stainless steel rod.

First exposure tests

Here are some images of my first exposure tests. This is 8% gelatin with 20mL isopropyl alcohol and 5mL of 1% alum. Poured at 0.035″ using magnetic strips as a dam. Gelatin was leveled with a heated 5/8″ rod.
Sensitized with 4% ammonium dichromate 1:1 with isopropyl alcohol (2% total) at 7mL total or 0.125mL/sq in. This amount seemed excessive for only a single coating.
There appears to be good detail at the 15 min exposure, but I will retest tomorrow with a more detailed negative at 12, 14, 16, 18, 20 min.

Exposure times 5-30 minutes:

cabin_testHere is a closeup of the relief after soaking 30 min in clearing bath:

cabin_closeupAnd here is the same image done in palladium on COT 320 paper using the exact same negative:




First papers

I have decided to begin oil printing with Fabriano Artistico Hot Press paper of 300 gsm weight. First, I begin by stretching the paper by soaking it at room temperature for five minutes. I found this large 28″ x 30″ tray at Lowes hardware store. it is intended as an appliance drip pan and was only $28.



After soaking, I fasten the sheet to a stretching frame I built from hardware store materials.


When dry, I add a sizing to the paper by brushing on two coats of Liquitex Fluid Matte Medium diluted 1:1 with distilled water.



The following day, I coated the papers with an 8% solution of gelatin. The mix includes:

80gm gelatin (250 bloom)

20mL isopropyl alcohol

5mL of a 1% solution of chrome alum

distilled water to make 1 liter


I coat the mixture onto the paper as follows:

Soak paper in room temperature water.

Squeegee wet paper onto sheets of pre-leveled plate glass and galvanized sheet metal on top.

Lay a framework of 0.035″ magnetic vinyl strips just inside the edge of the paper.

Pour the gelatin mix, heated to 110F, over the paper and spread with a heated stainless steel rod.

Remove the magnetic strips, squeegee off a 1/2″ strip of gelatin on both short sides, and hang to dry.