Originally Posted by donbga
I have a Honewell HCM-300T, or maybe it is the HCM-310T. It is a tower like unit that sits on the floor. I am able to close off my working space to house heating and that way the space easily stays at 60% or more RH running only about 30% of the time.
Here's another suggestion. Do a pre-coat of distilled water, and then dry it in the same way you normally dry the coated emulsion. After the paper is completely dry, you can proceed to coat it with the Van Dyke solution, which should penetrate more evenly and completely. Using a 1% solution of Oxalic acid is also another common technique.
Most of the papers we use are hot-pressed and have a very hard surface, and most have some sort of surface sizing applied. These papers are acid-free, which means and alkaline buffer (usually Calcium Carbonate or similar) has been applied to the paper giving it a high pH. Using oxalic acid will neutralize the buffer, and help keep the acidic VDB solution free from contamination by an alkali.
On a side note, Howard Efner has found that adding 1 or 2 drops of .25% oxalic acid solution to a 4x5 or 5x7 size print will increase the contrast and D-max. VDB solution made using green ferric ammonium citrate didn't show as much increase.
The pre-coating solution also serves a dual purpose, in that it will swell the surface fibers of the paper, helping them draw the VDB solution into them. You don't want the solution drying on the surface of the paper, or in between the fibers, rather you want each of the individual cotton fibers to act like a little capillary and hold the solution inside it.
In the winter time it's difficult to keep both the temperature comfortable and the RH at a high level, so I recommend pre-coating to many of our customers in colder northern climates. I've found that it helps Arches Platine a considerable amount, as well as the Bergger COT-320.
I'm starting to ramble a bit, but I hope I've made some sense in my logic.
Bostick & Sullivan
thanks for the tips Dana,
I am using rising stonehenge white.
They did not have arches platine in stock.
I will try pre coating today. also i'll crank up the humidifier
Originally Posted by Dana Sullivan
I just want to say I think it is nice to have some from B&S contributing to the APUG forum. I am aware that you folks have a large data base of information about alternative printing and it is really great to have you come here and share it with new printers.
And please say hello for me to the other Sullivans, all great folks.
I use a cheap watercolor brush that is dampened with water. I also add a drop of glycerin to the solution, it helps me with uneven coating. I'd love to try some gum arabic but it's kind of expensive around here. The glycerin is cheap.
I use Crane's kid finish ecru white. Good stuff!
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