[alt-photo] Re: applying VDB etc. emulsions

Earl and Patty Johnson earlj at comcast.net
Tue Oct 12 09:45:22 GMT 2010

Following Mike Ware's recommendations, for argyrotype or cyanotype I use a small plastic syringe to measure and apply the sensitizer - 3.0 to 3.2 ml is just right to coat an area 10.5" x 14.5" on 11x15 paper. The glass rod is 10.5" long. The syringe allows me to deposit a consistent bead of sensitizer across the sheet just in front of the glass rod. I like to use just enough sensitizer that 5 passes almost uses up all of the liquid (3 down, 2 up). The last pass I pull the little left over bead of sensitizer onto the blue masking tape at the bottom of the sheet, where I can swipe it with a paper towel. This coating gives me room to place an 8x10" negative along with a 31 step Stouffer wedge. With a glass rod, the coating defects are usually out at the ends of the rod, or at the beginning or end of the pass, so I like to make sure that I have coated sufficiently outside my printing area. If I am using gold toner, I cut the border off the sheet before it goes into the toner, so I don't tone more than I need to.

Different papers use different amounts. Humidity makes a difference, as does the use of Tween in the mix.

Earl Johnson

On Oct 11, 2010, at 9:03 PM, david drake photo wrote:

> Ken,
> The puddle pusher works great in that you get an even coating and use less sensitizer but your negatives have to be a consistent size  (to match up with the negative) or else you end up with massive borders.
> I measure out the sensitizer into a shot glass and then pour onto the paper. That way there is a consistency of amount. The amount is relative to the type of paper and the humidity of the room/paper; it's something you just have to figure out for yourself, overt time. However, when I use a brush, it should only take around 10-15 seconds to brush on or I'm using too much sensitizer.
> I have been using 0.5 ml for a 6 x 7 inch area (Arches Platine paper in 50% humidity) . Less is better.
> david
> On 11-Oct-10, at 9:30 PM, Ken Sinclair wrote:
>> For years I have been applying Cyanotype, VDB etc emulsions to the paper with either
>> a hake brush, a sponge brush or a 2 inch watercolour 'flat'.
>> Recently, I seem to be getting a somewhat  uneven application resulting in the more than
>> occasional 'darker line' along the 'length' of the paper which seems to be evident after brushing
>> across and somewhat obvious before exposure...    but is not that apparent after exposure and
>> processing when the print come out of the final wash.
>> Since I apply the emulsion to several sheets at a time, I do not have an accurate account of the
>> volume I have been applying for either 4x5 or 8x10 prints since I use a small container for
>> the 'batch'.
>> I am now changing over to a glass 'puddle pusher' and would appreciate some advice on the
>> volume either in ml or 'drops' for both 4x5 and 8x10 negatives.
>> TIA
>> Ken
>> Quando omni flunkus moritati (R. Green)
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