Chapter Four

XRF Analysis and Micro Fading

During the description and condition reporting phase for The Key, it was analysed using our portable XRF probe. XRF is X Ray Fluorescence. It is a non-destructive test and works by firing X-rays of a known energy level at a sample, which then reflects X-rays of a different energy level back to the probe. Every chemical element reflects X-rays of a unique energy signature, so the probe can tell you what elements you have in your sample by what X-rays it is receiving back. The way it works is that X-rays from the probe knock an electron out of the lower rings of atoms in the chemical elements of the sample; another electron from a higher ring then drops down to fill the gap, and the energy released by the electron dropping down is received and recorded by the XRF probe.

Photograph of Portable XRay Fluorescence handset

The Archives' portable XRF probe

The analysis of The Key gave us a strong iron (Fe) reading, which confirmed our assumption that it is a ferrogallic print.

With the Centenary of Canberra coming up in 2013, and the desire for the Archives to exhibit the Federal Capital Design Drawings, it is vital that we develop a better understanding of how stable all the entries are in light. Red inks are known to be vulnerable to fading, as are dye-based stamp pad inks. Paper supports will darkened with age, and we wanted to see if this would be further affected by light exposure too. The opportunity was taken during this testing to establish the stability (or otherwise) of Item 51.

The technique we used for measuring the colour change of the dyes and pigments on exposure to light is Micro Fading. In the micro fading process a tiny beam of very strong light is directed at a material and its fading behaviour is recorded. The spot tested is microscopic and the fading is only allowed to progress as far as one ‘just noticeable fade’ – the minimal colour change discernible by the human eye.

Microfading being undertaken on a Griffin painting

Bruce Ford, consultant Conservation Scientist, undertakes micro fading tests on a Griffin painting in the Archives’ Conservation Lab

The areas tested on our print were the paper itself (to measure darkening rather than fading), the ferrogallic image, the red ink, the black ink and the graphite pencil.

The graphite pencil and the black ink were shown to be stable. The image lines and the paper did change colour, but not dramatically, but it was the red ink that produced the most significant result. The red ink falls into the category of having a “high responsivity to light”.

Once the result for the red ink was in, the stamp pad inks were not tested as it was apparent already that the red ink would be the limiting factor for any display.

The reactive nature of the red ink to light means that if the print were to be displayed, it could only be for a limited amount of time (no more than six months) and during that time the light levels would have to be low (no higher than 75 lux with no UV content).

Chapter Three

Discoveries on Closer Inspection

A first glance at “Key to Accompanying Perspective View from Summit of Ainslie” (hereafter referred to as “The Key”) shows a simple ferrogallic print with red ink annotations on very discoloured paper. Closer examination, though, reveals that there is a lot more to this particular print.

Firstly, it is 2362mm long and 715mm wide, so it is rather large!

Cheryl examining the print

Cheryl Jackson examining The Key under the microscope

The red ink annotations appear to be in two different ink tones, but when examined up close, it is actually the same ink. Some of the annotations are written directly over graphite pencil under-drawings, which cause the red ink to look darker. These graphite under-drawings are generally associated with the written annotations, but there are instances of them as stand-alone annotations. For example, in the image below, the word “Forum” can just be made out between the words “Justice” and “Water”. There are also black ink corrections where the original ferrogallic lines have been removed (by scraping) and redrawn.  

Red ink and pencil annotations on print

Red and black ink and pencil annotations

In the next image you can see a partially erased title for the print, lower centre, in freehand script:

Pencil annotation on print

Pencil annotation, partially erased, giving title of print

Even the remnants of this script must be carefully avoided during surface cleaning so that they are not removed.

An interesting aside, which illustrates the haste the Griffins were in to get The Key to Australia, is a spelling mistake in one of the annotations. The word “Railway” appears as “Ralway” and has not been corrected.


Misspelling of "Railway"

Further to the annotations applied by the Griffins themselves, there are several registry stamps and descriptions written in ink and pencil on the outside edges of the print, which would have been visible when the print was rolled.

Stamp and various inscriptions

Stamps and later annotations on back of print

There are two areas of staining from strips of masking tape applied to the back of the object, holding torn sections together. Curiously, these stains on the front do not correspond exactly with the position of the tape on the back. Rather, the staining has occurred when the object was tightly rolled and the masking tape carrier came into contact with the front of the print.

All these different inks add character to the item, but they also inform the treatment proposal. If any of these inks are soluble in water or organic solvents, then those solvents cannot be applied to the object. Fortunately, after solubility testing, the inks do not appear to be water soluble, so if moisture has to be introduced to the object in the course of the treatment, the inks should not be affected.

The pencil under-drawings mean that any surface cleaning with erasers has to be extremely carefully carried out so as not to remove these original lines. The surface cleaning will be undertaken with two different approaches – one for broad area cleaning and one for fine, detailed work (stay tuned…).

Chapter Two

How “The Key to Griffin’s Canberra” was made

Now for a bit of an explanation about what type of object the ‘lost’ Griffin image (NAA: A710, 51 [Competitor number 29 Walter Burley Griffin – Perspective] View from summit of Mount Ainslie [Part D]) is.

As far as we can ascertain from studying and analysing the image, it is a FERROGALLIC print. This means it is a positive print (dark lines on a light background) made from an original drawing on translucent tracing paper (see below for more information). Ferrogallic prints were a handy process as they produced a positive print from a tracing without needing an intermediate negative step.

The ferrogallic process was developed in 1860 and was in use at the same time as the much more common (and recognisable) blueprint process. Both print types have iron as the basis of their images.

Example of a Blueprint Example of a Ferrogallic Print

(Left) Blueprint. NAA: B3712, Drawer 8 Folder 4: (Right) Part 2 Ferrogallic print. NAA: J3088, QPT501

There were two different methods for making a ferrogallic print. One was used in the early stages of the development of the process, and a more advanced system came into existence after 1900; our print was produced in 1912*, so it is fairly safe to assume it is the later method. In this process gelatine or gum arabic is mixed with ferric (Fe3+) salts (usually iron chloride or iron sulphate) and an organic acid (tannic or gallic acid) and applied to a sheet of paper. This sensitized paper is exposed under a tracing to an ultraviolet (UV)-containing light source. The UV light reduces the ferric salts to a ferrous state (Fe2+) which is soluble in water.

After exposure, the paper is washed in water which releases the organic acids, creating an acidic development bath. The water soluble gelatine (or gum arabic) and ferrous salts are washed out of the print, while the acid bath coverts the ferric salts to a ferric gallo tannate pigment which stays behind in the paper and forms the image. This image is almost the same (chemically) as iron gall ink.

When the prints are first produced they have a black image on a white background, but as they age, the image fades and the paper darkens (thanks to the acidic bath mentioned above) and the contrast between image and paper becomes very low.

The acidic processing bath also contributes to making the support brittle. Paper is made up of cellulose molecules, which, simply put, are chains of glucose molecules joined together by an oxygen bridge. The residual acids in the paper support attack these bridges and cause the cellulose chain to break apart. As the chain breaks down, it loses flexibility. This decrease in flexibility manifests in the paper sheet as brittleness. The paper fibres can no longer bend and flex, but break instead.Loose fragments of Item 51

Ferrogallic prints have never been known for their longevity. A life span of 30 years* has been predicted for them, and our print is now 100 years old. No wonder the poor thing is fragile!

*Kissel, E. and E. Vigneau, Architectural Photoreproductions: A Manual for Identification and Care, Oak Knoll Press, 1999, p46.