Weston diploma parchment paper: Test results

Mike Ware tests palladium, platinum, platinum/palladium, new cyanotype, new chrysotype and argyrotype printing on Weston Diploma Parchment.

Writer / Mike Ware

N.B. The following methods of iron-based (siderotype) printing used for these tests are those that I have developed personally, and are fully described on my web pages: http://www.mikeware.co.uk. These methods are not used by all printers, some of whom prefer traditional methods, which usually involve heat-drying the coated sheet, and otherwise using chemistry that performs as development processes. So the findings and conclusions of others may differ.

My methods are, as far as possible ‘printing-out’ processes (POP), in which the paper sheet, after coating with sensitizer solution is NOTheat dried, but allowed to retain a degree of humidity (usually in an atmosphere of R.H. ca. 60-70%). As a consequence, these printing methods are very sensitive to hostile substances in the paper, which have greater opportunity to cause deleterious effects than in the dried sheet. These methods place quite a severe test on paper purity, and are therefore quite “choosy” about which papers will work for them. E.g. many modern ‘fine-art’ papers, which are buffered with chalk, are very unsatisfactory unless subjected to some chalk-removing pre-treatment, which is tiresome.

All the following tests were carried out in a side-by-side comparison with my usual print-making paper – Buxton paper, which is handmade to my specification (see my web pages) by Ruscombe Mill, at Margaux, France: http://www.ruscombepaper.com/. Buxton paper sets a standard of excellence in its performance with all these processes but, being handmade from the finest cotton, it costs about ten times the price of the Weston paper!

General Features of Weston diploma parchment paper

The manufacturer describes the paper as follows:

• furnish: 100% rag denim
• weight: 177 g/square meter
• no optical brightener
• no alkaline buffer
• rosin-alum sized
• pH 5.5 to 7.5
• available in sheets 22″x34″ and 28″x34″

Weston Diploma Parchment has a very smooth surface on the ‘felt’ side, which is retained even after extensive wet processing – unlike some heavily calendered commercial papers. The processed sheet dries satisfyingly flat without cockling or curling, and there is no need for pressing. The ‘wire’ side has a perceptibly less smooth texture, but does ‘work’ also.

This paper coats easily and economically with all my sensitizer solutions using the ‘rod-coating’ method. The specific coating volume needed is ca.22 cc. per square meter. The paper is sufficiently absorptive of aqueous solutions not to require the addition of any surfactant (e.g. Tween) or wetting agent to the sensitizer solutions. Indeed, the effect of this can be deleterious. The colour is an attractively warm ‘cream’ hue, which will satisfy most tastes – but, inevitably, not all!

Palladium

Print-out Palladium is a robust process which works well with many papers, and Weston is no exception. Arange of smooth, well-graduated tones are obtained across the exposure scale with a good Dmax. (maximum density), and pleasant colour, depending on Relative Humidity. One drawback is evident on close inspection: there is a very slight, but perceptible, pale grey chemical fog in the unexposed regions, accounting for a slight background density. This is presumably due to a small amount of some hostile ingredient in the paper pulp, possibly a reducing agent, causing a very slight deposit of metal. This is not pictorially unacceptable, but it does prevent achievement of a pure ‘paper white’ for specular highlights. The effect tends to worsen with longer drying times.

Platinum

Pure 100% platinum printing, by the POPprocess, is a method that only succeeds on a few papers today: precipitation of the image metal is very easily inhibited chemically by a variety of papermakers’ additives, which are used in most modern papers. I’m encouraged to note that this paper does ‘work’ with pure platinum, and the Dmax is good, but the areas of uniform tone are not as smooth as might be wished – due to a fibrous ‘patchiness’. Is a mixture of different fibres used to furnish the pulp? However, the slight chemical fog noted with palladium is not evident with platinum, which is less sensitive. Colour with platinum is a good neutral grey-black.

Platinum-Palladium

This compromise mix (I used it at 1:1) is popular with many workers, and it overcomes the problem noted above with pure platinum: – tones are very smooth, Dmax and colour, a rich sepia, are good, and tonal separation is very clear throughout the scale. The background chemical fog is now only very slight.

New Cyanotype

This process is a very sensitive test of paper purity: any traces of reactive chemicals present in the sheet will cause an obvious background blue fog in regions that have received no light exposure. (It takes very little of the strong pigment Prussian blue to become visible!). In view of the slight fog noted with palladium, it’s no surprise that there is also a chemical fog with the new cyanotype process. However, unlike palladium, much of this can be ‘washed out’, and the pictorial results are generally quite acceptable; the colour is bright, and the tones are smooth, and well separated, with a good Dmax.

New Chrysotype

The paper works quite well with the process at a ligand to gold ratio of 4, and 76% RH, giving a bluish-black hue; however there seems to be some mottling evident in the mid- tones. When heat dried, the process yields a split scale with bluish-grey high values and dull purple mid-tones and shadows. Textures are quite smooth, but shadow tone separation is rather ‘blocked up’. There is no evidence of chemical fog.

Argyrotype

The nanoparticle (colloidal) silver image formed in this process is very vulnerable chemically, and easily lost during the processing on many papers if it is not protected within the cellulose structure. Image loss is the problem here with Weston paper: small patches of silver dissolve out during the fixation; but shortening the fixing time results in dark inclusions within the paper sheet. It is not possible to find a compromise, so the paper cannot be recommended for this process.

Summary of conclusions

Weston Diploma Parchment paper provides a very acceptable substrate for the print-out palladium and mixed palladium-platinum processes, and can be used with the new cyanotype and chrysotype processes. It yields good tonal gradation and maximum density. Its advantages of low cost, fine surface, and easy coating, wet-processing, drying, and handling would recommend it for workshops and teaching purposes. The only evident defect is the presence of a small amount of substance that causes a slight chemical fog in the sensitized coatings (- a background density that may sometimes pass unnoticed).

Website: http://www.cranepaper.com/
For supplies of this paper contact:
John M. Zokowski , Butler-Dearden paper Service Inc., 80 Shrewsbury Street, PO Box 1069, Boylston, Massachusetts, MA01505-1669, USA
Telephone: 508 869 9000 or 413 247 9073
Email: jzokowski@comcast.net

Written by Mike Ware, Buxton, October 2008.
This review was published in the Siderotype Report Issue Number 1, January 2009.
Mike Ware is a british chemist and inventor of the New Cyanotype process – amongst others and an author of many books.
Note: The tests were performed on the original Weston Parchment paper. Paper manufacturers change their products all the time, so test one or two pieces before buying a large batch!