Drawing technique in Ken Follett's The Pillars of The Earth

[Christiaan]

Random one for you. In Ken Follett's book The Pillars of The Earth he describes a drawing technique used by the main character, Tom Builder.

He would fill up a wooden tray with lime plaster and then, once hardened, use a sharpened-wire as a drawing instrument to scratch his drawings into it. "The scratch marks were white and clear when first made, but they faded grey, which meant new drawings could be made on top of the old ones without confusion."

Is Follett describing an historical tech drawing technique here or is he making it up?

[Robert Anderson]

Sounds like "silverpoint". See:

http://www.silverpointweb.com/overview.html

[islandmon]

Part of the curriculum at Art Center> gesso on canvas board > render with silver point pen tool.

My mother still cherishes the 'silver point' rendering I created from an old Kodak of her childhood home in Montreal.

[Benson Shaw]

The plaster "tracing" surfaces and full tracing rooms with plaster floors hosting drawings and setouts seem to have a different technique than silver point. These are incised lines. But, perhaps silverpoint was also used, or was indeed the source of the inscribed lines still found at Wells Cathedral and many other structures.

My brief online search did not find confirmation of Follet's assertion that the wire scribes in lime plaster yielded a dark line which faded to "clear" the slate. I hope others can illuminate this.

Thanks, Christian for bringing it up.

-B

[Benson Shaw]

Still no historical confirmation, but here is an opinion from an industrial chemist:

The technique described by Follett of fading linework on lime plaster is quite plausible:

Lime plaster is primarily Calcium Hydroxide Ca(OH)2. I believe that wires of copper, zinc, lead and other alloys would have been available at these cathedral construction sites. Sand or other abrasive in the plaster scrapes off bits from wire without incising the surface.

Ca(OH)2 reacts quickly with the metal (directly with the wire or the scraped off bits) to form precipitates of metal hydroxide - typically a dark color. Thus a line appears without incising the surface. The metal hydroxides are somewhat unstable and react at various speeds with oxygen in air or residual moisture in the plaster to form metal oxides. The oxides of lead and zinc are white and would therefore seem to disappear or fade, leaving an apparently blank plaster surface. Copper oxide is rather dark so not a good candidate for this process. Formulations of the plaster and metal wire would offer some control over reaction/fade time. A self erasing white board!

I will try to acquire a batch of lime plaster and give it a whirl.

German chemist Raphael Liesegange explored these types of reactions on paper and other media around 1900 with interest in the bleeding of the line away from the center (Leisegang Rings). Contemporary chemists are elaborating on these findings, in the field of paper chromatography for instance.

-B

[Christiaan]

Wow, cool, is this chemist a friend of yours? Look forward to hearing about his results.

In the mean time I've gone and asked Mr Follett himself. No response as of yet.

[Christiaan]

Well here's his response: "It's real." No references unfortunately.

[Bob Holtzmann]

I would surmise that this drawing method would have been used mainly for sketching in place on plaster walls for fresco painting. They both date from the Renaissance.

Although, I do recall that for the Sistine Chapel ceiling, Michelangelo used paper drawings with perforated outlines for transferring his sketches, by dusting a charcoal filled bag over the surface of the perforated paper.

[Benson Shaw]

Yes, chemist is a friend. He is a materials scientist working on non-portland cements which require/absorb CO2 during cure/set.

I am slaking my lime. It may take a couple months. Will report.

Any additional experience welcomed.

-B

[Christiaan]

By the way, I ended up using Follet's description "needle and mortar" to name this new website: http://needleandmortar.com/ ...thought it had a nice ring to it.

[Benson Shaw]

LIttle update: My hydrated lime hardens to a softish but drawable surface, with and without sand. Drawing or even scratching with zinc, copper, steel produces no mark, wet or dry, sand in the mix or not. Didn't have any lead to try, although it seems too soft to be a likely candidate for a "sharpened wire" unless in a pencil type holder. I will get to that, too.

I'm making carbonized samples next by addition of ground marble (Calcium Carbonate). This should make harder samples and could also turn the mix grey or dark so that the lines could be white initially (oxides?) and then fade to dark (hydroxides?)

It's an approximate test. Lots of variables with no control and I'm just guessing at what was available in the "historic" recipe. The easily available materials I am using are manufactured to be very pure. My lime is bright white. Tom Builder may have had local impurities and therefor a darker base color. Or maybe it had marble dust in it.

Stand by.

-B

Edited October 12, 2010 by Benson Shaw

[Christiaan]

Here's another line from the book: "Then he burned some chalk for lime, mixed up a small quantity of strong plaster, and filled the tray with the mixture."

[Benson Shaw]

Thx - I'm still trying to figure out if the whole plaster is dark, or a dark surface layer (oxidized?) on a white base. If dark surface, the scratching would reveal lighter color beneath which could then react with air/moisture to return to dark. The plaster could be damp or even mushy wet, too. A quick trowel or wipe would remove incised marks.

Anyway, still horsing around with it. Lots to try. I've put out some requests in the lime and historic restoration industries. Will report.

Anyone else with experience or sources is welcome to "solve" this mystery.

-B

[Benson Shaw]

So far no success in my tests, but maybe some promise.

I posted the info to a British lime dealer who said Follett has it half right - A lime surface could be dark so that scratching with a nail would reveal an underlying white color. But this would be static - no self fading in his experience.

The afore mentioned chemist friend has a demo project with his non-portland material. The surface of the wet mix changes color with exposure to air. Disturb or scratch though the surface to reveal the lighter, "fresh" color underneath. This newly exposed area soon changes color to match surrounding surface color. Proves possibility of Folletts assertions. But completely different materials, and color difference is slight. After cure, the whole mass takes surface color.

I will carry on with some new lime and more questions to the regional lime industry.

-B

[Christiaan]

Thanks for the update Benson.

[Benson Shaw]

HI, Christiaan et al reviving a waaaay old thread.

OK, I give up for now. Sorry to report that I have not been able to recreate the scenario reported by Ken Follett regarding a self clearing lime plaster drawing surface.

I think the modern materials I used are just too refined or pure. Or maybe there is some new material to find or trick yet to learn. Anyway, I think the condition is more related to the plaster changing in response to atmosphere rather than some reaction with the metal stylus.

Two analogies make this seem likely:

Avacado dip - Turns brownish on surface layer. Swipe a chip through it and reveal the bright layer below. Wait an hour, and that turns brown, too.

Peruvian Land Drawings, or Nazca Lines - Eons of exposure oxidized the mineral surface. Push away the top layer of rock to reveal the unexposed, bright material beneath (or drive your ATV through it - grrrrr). Wait a few eons, and the new lines oxidize to uniform color.

(oh, great. Now he's blathering about Avacado Dip on the forum)

-B