January | 2014 | In the Artifact Lab

A previous post introduced you to this demotic jar, currently on view in the Lab. The first step in its treatment was to clean the surface, which was very black due to dust.

It was necessary to make some tests on the ceramic to determine which way to clean was the best, meaning the safest for the object. Indeed, the black inscription on the jar is fragile and water sensitive. The first rule was to choose a non -aqueous method, that’s why I first thought about…erasers !

Image showing cleaning tests on a fragment of the jar.

Test 1 : Sanford Magic Rub Eraser. Test 2: Staedtler stick eraser.Test 3 : Latex eraser.

Test 4: Ethanol

Test 5: Wishab eraser.

As you can see on the picture, the erasers seem to be the best choice, especially the n.2. Indeed, it can be applied with different levels of strength according to the amount of dust to remove.

Ethanol was also to be tried, being a “light” solvent; but the issue with a solvent is that you can’t control how it penetrates in the material, especially with a porous ceramic. So the best choice seemed to be the Staedler eraser.

It was then time to test this cleaning method on the inscription.

Cleaning test with the eraser on an inscribed fragment.

The eraser appeared to work well, removing only the black grime and not the inscription. Of course, one has to be careful with this method, and not to press the eraser too hard or the black ink could disappear as well !

So I went on and cleaned all the other fragments.

Fragment before cleaning.

The same fragment after cleaning.

In a general way, cleaning an object is very rewarding for a conservator, because the result can be seen at once. And pictures taken before and after are often impressive.

However, some things could not be improved; many demotic signs are lost due to water damage that occurred in the burial environment so the text isn’t complete. Moreover, a few fragments didn’t change after being cleaned, and still look dusty even if they aren’t.

Here is the general result, after all the fragments were cleaned.

General view of the fragments before cleaning.

General view of the fragments after cleaning.

Next step: de-gluing the fragments !

If you’ve been following the Artifact Lab blog you are now familiar with the two Egyptian wooden heads and the work in progress on them. Those heads are complex since they are composed of several materials that the conservator has to understand to treat them.

So let’s explore an important but now almost lost of their aspects: polychromy. Indeed, 99% of the colors on the heads are lost but some remains allow us to figure out what colors were originally theirs.

Mapping of E17910 red paint layer.

Let’s have a look at the real colors left on the heads:

E17911 – On the left: Detail of red paint on the left ear (x 10 magnification) ; On the right: detail of blue paint on the the wig located on the right of the head (x 10 magnification).

E17911 – On the left: detail of black paint on the the wig located on the right of the head (x 10 magnification) ; On the right: Detail of red paint on the left ear (x 10 magnification).

E17910 – Detail of the red paint above and under left eye and red paint below the right eye (x 10 magnification).

The wig is black (even if it looks blue on the picture !). The red is ochre, produced by reducing iron oxides to powder.

All Egyptian statues (and generally statues from other ancient civilizations) were completely painted. Only a few of them had their polychromy preserved, and it is especially rare on wooden artifacts because of many alteration factors that damaged these objects. The two heads were buried in a grave, several feet underground and the groundwater could rise very irregularly and completely overflow the tomb and its contents. The wood suffers a lot from humidity changes: indeed, this material always tries to keep its own moisture content stable, according to the environment moisture. That involves cycles of giving off and taking moisture; if those cycles occur too many times, the wood can’t follow and breaks generally appear.

If the wood is covered with a polychromy layer, it falls off since it can’t follow the movements of the wood. The wood is also susceptible to damage by other substances, like different types of salts and other alkaline substances whose action is increased by humidity.

That’s what explains that on the heads, the few areas of color left are in a bad condition; let’s try to explain what’s going on under the sediment!

To give you an idea, here is a stratigraphic representation of what a nice and undisturbed polychromy (if that exists!) should look like:

The wood is covered with a preparatory layer; it allows the surface to be even so that the paint layer can stick better to it. That’s it about the theory, let’s see what we have in reality:A lot less pretty and legible ! We can’t say whether the preparatory layer exists or not, and the paint is covered with a modern application of paraffin wax that wasn’t applied correctly on the wood; indeed the white material that covers some areas of the surface and of the polychromy is a paraffin deposit.

White paraffin deposits on the paint and the wood.

E17911 – The paint layer is poorly attached to the surface and termites didn’t spare it.

The paint layer is poorly attached to the wood and the paraffin used to strengthen the heads in the field (during the 19^th century) is the only thing maintaining them.

While we are grateful that there is still some polychromy remaining…paraffin isn’t such a good thing ! It will be the topic of a next post to come.

In the Artifact Lab

Monthly Archives: January 2014

Cleaning the jar

The heads in color.