Wet sizing with threading bar

The correct sizing procedure (left) consists in pouring gelatine on sheet (1) and laying it using a threading bar (2), to obtain a uniform cover up. If, on the contrary (right), the bar is on the sheet (1), when the gelatine is poured on it, it follows the threading bar (2) and easily oozes out of the sheet (3).

I always had hard times sizing the paper used for printing in a fulfilling way. That’s the reason why I always tried to avoid sizing my supports. If this is possible with the ferric salts and the one coat gums, it is a serious problem when you want to obtain clean whites with multiple dichromate gums prints.

I never obtained good results laying gelatine, as the brush raises bubbles and bristle streaks. Dipping always gave big and ugly dregs once hanged out the paper to dry. Moreover, it is necessary to harden it twice and dry it inverting the bottom with the top to obtain a uniform gelatine thickness on the entire sheet; otherwise the gelatine will be thicker on the bottom.

During the month of July Damiano Bianca showed me how to lay gelatine using a threading tube large as much as the sheet.

During last weeks I bought a tube like his, but a little bit more rusty because I couldn’t find it in brass. Not to get the paper dirty, I also bought a stainless steel threading bar. It can’t be filled up with hot water as Damiano does, but if I leave it in 50°C water, I think it is hot enough not to make the gelatine wrinkle.

During summer holidays, I bought a new type of gelatine and during last days I wanted to try my bar. Therefore, today I wore my gloves, eyeglasses and gasproof mask (formaldehyde is extremely dangerous for lungs, better avoid to inhale in large quantity), I took some failed gum prints and went into the dark room.

I didn’t remember if Damiano wet or not his sheet before putting gelatine on (I’m sorry Dam, my bad; you taught me so much stuff that I didn’t took note of this detail). I tried on a Rives BFK dry sheet but it embarked and gelatine accumulates into hollows, both on 56×76cm and the half sheet. I tried to flatten or agitate the sheet as when laying the oil inside the skillet, but the results have been a disaster.

Next I bathe another sheet for 2’ in water at 40°, the same gelatine temperature. Then I put the sheet on a pane with the image upwards and I rolled it to press the water out of the sheet and make it adhere to the pane, not to imbark. The gum image doesn’t seem to suffer for it. I dried water from borders using toilet paper. This detail creates a sort of dyke to gelatine, avoiding drops out of the sheet.

Unfortunately I think that in this period of time, necessary for all those operations to be done, paper gets cold and its temperature decrease. Anyway my dark room today was 23°C, so maybe it will be a winter problem.

As the sizing solution has been poured at the center of the image, the mixture is positioned in a uniform way on the entire paper surface, as well that only a couple of threading bar strokes were necessary to re-distribute it on the picture rectangle. I dried the borders with toilet paper again, for the reason that, if gelatine oozes outside and goes under the picture, it is impossible to take it off once hardened.

I left the print on itself for tent minutes to let the gelatine do its job, then I peeled it off, keeping the most horizontal position I could, and transferred on a surface covered with blotting paper. I should build a humpback net to let it dry on the back as well and avoid the central accumulation, but I use an absorbent surface for now.

The surface remained perfectly smooth, without bubbles or imperfections. The humpback net should give regular thickness as well.

The only feature is not to let gelatine oozing out of the sheet. I noticed that putting the bar on the paper and starting pouring the gelatine on it makes the gelatine follow the bar. It would be easy, once the bar is moved, that the gelatine ooze where the bar crosses the sheet borders. If the gelatine is poured in the middle of the sheet and then the bar is leaned, only the center of the paper can be sized, leaving the borders dry.

Among all the sizing strategies, this one of the wet threading bar technique is absolutely the most precise and efficacious. Well, you must humidify one sheet per time, paying attention not to stick it, waiting a certain amount of time before moving it, etc… But those who work with alternative techniques do not care about speed rather about the result. And that’s the reason why this is the best technique.

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