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

[Kerik]

Speaking of shrinking, I've found that the thinner versions of BFK (175
GSM, I think even though it's called Heavy) shrink less and are easier to
register than the thicker versions (230 or 280 GSM?).

Kerik
www.kerik.com

> Thanks so much for this info, Henry! And you even measured..
>
> My prints are too big to get away without preshrinking, plus I do not
> find that step horrible.
>
> I, too, found that the paper laid flatter with PVA vs. gelatin for
> some reason.
>
> Interesting the difference in shrinkage between the papers....
> Chris
>
>
>
> On Monday 03/22/2010 at 9:23 am, Henry Rattle   wrote:
>> 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
>>
>>
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-- 
Kerik
www.kerik.com