[alt-photo] Re: pre-shrinking and PVA size

[Henry Rattle]

Just finished some trials with PVA size on Saunders Waterford (300g
hot-pressed) and Fabriano Artistico (300g CP, traditional white). Starting
with virgin (not preshrunk) paper, the sequence was size, then (coat, dry,
expose, 1 hour in water at about 20C, develop with spray, dry) for each of
three coats of gum/pigment.

In passing, I measured shrinkage. After the treatment above, the FA shrank
0% in one dimension and 1.1% in the other (across the 12x9 sheets I was
using). The Waterford was 0.4% in one dimension and 1.2% in the other.

My normal print size is about 9x7 inches, so a 1.1% shrinkage on the short
dimension puts me about 0.8 mm (sorry for mixed units) out of register at
the top and bottom edges of the print, assuming I register for the centre.
Whether this matters to you depends on the subject matter, I guess - but I
think I'll continue to preshrink my paper, though not in hot water.

As to the Gamblin PVA size, I was very pleased. I coated successive 3 inch
wide strips of each single sheet with full-strength, 1+1 and 1+2 PVA size,
then coated and developed three-colour gum as above.

The full-strength PVA, though I tried to coat thinly like Diana, had a few
patches which were hard to coat. It also had the slightly plasticky surface
that Diana objects to.

At 1+1 both the Saunders and Fabriano coated easily and cleared very well.

At 1+2 the Fabriano cleared well and the Saunders not quite so well. Both
cleared better than my control sheet, which was Saunders which had been
brush sized with gelatine/formaldehyde. That was my standard till today, but
from now on I'll be using FA/PVA.

The other plus for the PVA was that there is far less of a fierce curl on
the dried paper than you get with gelatine, either brushed or soaked. Much
easier for the next coat.

With best wishes

Henry