Au revoir, Laura!

Since September, we have been very fortunate to have Laura Galicier interning with us in the Artifact Lab. Laura is a graduate student studying conservation at the University of Paris Pantheon-Sorbonne, and spent her time here working on the conservation of several objects, two of which (the wooden heads) are the basis for her dissertation.

laura with headsLaura will soon graduate with her degree in conservation, and will embark on the next phase of her career as a conservator.  Although Laura’s final day in the lab was last week, have no fear – you haven’t heard the last from her. She has at least 1 more blog post to contribute, which will be available soon.

Congratulations, Laura!  Félicitations!  We will miss you. And these guys want to know, when will we see you again??

heads goodbye laura

A new material in the Lab

loadimg.phpWhile we primarily work on Egyptian materials in the Artifact Lab, we occasionally work on objects from other cultures as well. (http://www.penn.museum/sites/artifactlab/2013/12/21/ch-ch-changes-in-the-artifact-lab/) Recently, two new objects were brought to lab. They are two glass vessels from Cyprus, which were discovered in the archaeological site of Kourion. Their date is unknown.

Untitled-1Capture

First of all, what is glass made of? Generally three materials are mixed together:

- A former, being the main component: silica, usually found in sand;

- A flux, lowering the melting point of the glass mixture, the melting point being the temperature at which the glass mixture becomes a liquid (from 1600-1713 Celsius for raw silica alone to 800 Celsius for silica + a flux); this material is an alkali or soda.

- A stabilizer, inserted inside the chemical structure of the glass to strengthen it; usually lime.

- A fourth material, metal oxides, can be added to obtain a specific color (manganese for purple, gold for red, silver for yellow…).

This composition and the percentages of each substance change according to times and places. Moreover, glass can take a wide range of different shapes.

Here is a picture of the objects before treatment:

The two glass objects before treatment.

The two glass objects before treatment.

Both are glass vessels. The vessel on the left was restored in the past; a coating was applied on its whole surface and it was glued with that same substance. This adhesive is now flaking off the object, leaving thin and transparent films. This become more obvious when observed under ultraviolet light.

The object viewed under UV light. The bright white-yellow material is the old adhesive.

The object viewed under UV light. The bright white-yellow material is the old adhesive.

The old adhesive is pretty obvious now, with its white-yellowish color. This substance is also soluble in acetone. These properties allowed us to conclude that it is cellulose nitrate, a well-known material used to restore glass objects in the past. In addition to not aging well, this adhesive was applied very thickly on the edges, preventing the fragments from being joined together correctly.

Example of a problematic cellulose nitrate deposit on the  edge of a fragment.

Example of a problematic cellulose nitrate deposit on the
edge of a fragment.

Both glass objects also show evidence of delamination of their surfaces. It takes the form of a white layer, which flakes off the object.

New Picture (3)This phenomenon, called delamination, can start in the burial environment especially when the object undergoes weathering. This weathering changes the refractive index of glass as well. Each glass artifact has a specific refractive index, indicating how the light passes through it. According to this, our eye will perceive the object a certain way. Any change in the material, such as delamination, will alter this refractive index and thus our perception of it.

Untitled-10Here is an illustration directly on the object itself:

Delamination of the glass; the delaminated layers are white whereas the ‘glass substrate’ show a brown amber color.

Delamination of the glass; the delaminated layers are white whereas the ‘glass substrate’ show a brown amber color.

This process, if not stopped, can end up delaminating the whole object, layer by layer, resulting in the loss of this artifact. Conservation treatment, and good environmental controls, can prevent this from happening.

We’ll write more about the treatment of these glass vessels in our next post!

 

 

 

The jar is gone !

Example of an Egyptian jar, complete (XVIIIth Dynasty).

Example of an Egyptian jar, complete (XVIIIth Dynasty).

After making some fills on the Egyptian demotic jar, two other steps remained to complete the treatment.

First: painting the fills. The goal is to tone the fills with a color matching the general shade of the ceramic, so as it doesn’t catch your eye when you’re looking at it from a few feet away. It has to be clearly distinguishable if you get a closer look.

Here is the result:

Untitled-2 Let’s have a closer view:

Untitled-3

Untitled-4

View of the 4 areas of the jar that were filled and toned.

Second step: making a storage box. The basic rules about storage-making are quite simple. The materials used to make the storage must be chemically neutral towards the object and their ageing must not threaten its condition. For example, some materials can deteriorate in a short-term time period and cause chemical reactions with the artifact they are supposed to protect, causing alterations.  That’s why conservators use materials that were approved by testing them, like submitting them to specific temperature or humidity settings. More details about storage materials can be found following this link.

To prevent this situation from happening, acid-free paper and cardboard, polyethylene foam and fabric, and other well-known conditioning materials are preferred.

Then, each object being different, the storage needs to be adapted to its needs (size, weight, material sensitivity…) but also to the room available in the storeroom itself ! Concerning the jar, it was about allowing its safe and easy handling and preventing it from rolling.  According to its weight, the cardboard used had to be quite strong.

Left: the box has a front side that opens and a small compartment (on the right) to store fragments that couldn't be glued to the jar.   On the right: The box with the front side closed.

Left: the box has a front side that opens and a small compartment (on the right) to store fragments that couldn’t be glued to the jar.
Right: The box with the front side closed.

The mount, so as the jar can safely be pulled out of the box.

The mount, so as the jar can safely be pulled out of the box.

Left: the jar in its new storage box... Right: ...ready to go back to the Egyptian storeroom.

Left: the jar in its new storage box…
Right: …ready to go back to the Egyptian storeroom.

Here ends the conservation treatment of the jar; it was brought back to the storerooms last week. But we still have new projects in the Lab !

A new challenge in the lab

I am always pleased to see returning visitors to the Artifact Lab. And of course, people who have been here before want to know, what’s new? Visiting the lab is the best way to find out about our latest projects and progress, but this blog is the next best thing.

So, what is new around here? Well, I’ll let you take a look for yourself:

shabti boxThis object was featured in the “What in the World” series on the museum’s Facebook page this week. There were a wide range of guesses as to what this is; my favorites being a breadbox, an Egyptian mail box, a papyrus organizer, a holder for cat mummies, and an ancient Egyptian Matchbox-car garage.

Seriously though, this is a shabti box. Here is a shabti box that is similar in style, at the British Museum. Shabti boxes were used to house shabti figures. Shabtis were included in burials as servant figures that would carry out heavy work on behalf of the deceased. They were depicted as mummified and were inscribed with spells which, when recited, magically caused them to come to life and perform work for the deceased in the afterlife. Here are 3 shabtis that were originally housed in our shabti box:

shabtisThe shabti box and shabtis are made of wood, covered with a thin layer of gesso, and painted. They are in the lab for treatment because their surfaces are actively flaking. Not only is the paint flaking, but there is a yellow-orange coating over the painted surface that is badly flaking as well.

This yellow-orange coating is applied over the entire surface of the shabtis and the box (inside and out), and it is very thick in areas.

A detail of the shabti box showing areas where the coating is particularly thick (pointed out here with the red arrows).

A detail of the shabti box showing areas where the coating is particularly thick (pointed out here with the red arrows).

My first question is, what is this coating? Is it an original varnish or is it a later restoration?

The box and the shabtis date to the New Kingdom, ca. 1200 BCE. We know that varnishes such as those containing pistacia resin were used on painted wood in the New Kingdom, and these varnishes often appear yellow, although they may not have been yellow when first applied. We also know that these varnishes were applied unevenly – the application of the pistacia resin varnish has even been described as “messy” and it is acknowledged that its purpose was not an aesthetic one, but rather intended to make such objects more divine, or suitable for the afterlife (Serpico and White 2001). This description may help explain the rather sloppy appearance of the yellow-orange varnish on our shabti box and figures.

We cannot, however, discount the idea that this coating may be a later restoration. We know that archaeologists frequently stabilized artifacts in the field to allow for their safe recovery. Materials such as paraffin wax, gelatin, shellac, and cellulose nitrate have been used for this purpose in the field or once the objects found their way into museum collections (like the wooden heads Laura has been working on).

There are several ways in which we can try to determine what this coating is and when it may have been applied. We already have some clues, but we’ll share those in an upcoming post. Stay tuned for updates as we learn more!

 

Ungluing, re-gluing and filling the jar.

Statuette of an egyptian potter at work (beginning of  the 2nd mill. B.C).

Statuette of an egyptian potter at work (beginning of the 2nd mill. B.C).

The next step for the Egyptian jar was un-gluing all the fragments …to glue them together again.

We had two different cases: fragments that remained adhered together and fragments that were already separated, bearing remains of an old adhesive on their edges. The old adhesive had to be removed since it had many negative issues. First, it prevented the fragments from being joined back together by creating an unnecessary thickness at their junction. Moreover, when reconstructing the ceramic, the old adhesive prevents the fragments from fitting together well.

This old adhesive had a light brown color and after a few tests, it was found to swell when warm water was applied on it.

Here is what it looked like:

Detail of the break edge of one of the fragments, after applying water steam.

Detail of the break edge of one of the fragments, after applying water steam.

To remove the adhesive from the break edges, we used a Preservation Pencil, a tool looking like a pen and emitting water steam. Once softened, the adhesive was very easily removed with a scalpel or a brush.

And here is the result :

The same fragment edge after the removal of the old adhesive.

The same fragment edge after the removal of the old adhesive.

For the fragments still adhered together, it was a little more difficult since the water had to penetrate inside the jar but not too much because of the water-soluble ink on the surface. Compresses, or poultices, of water were applied on the interior of the ceramic, to cover the breaks. Most of the fragmentsfell apart quite quickly contrary to areas where the jar was very thick.

Now the building could begin ! … well almost since it was necessary to plan precisely how to proceed and in which order to arrange the fragments. First, we had to find where each of them was going, to estimate the losses. For that purpose every fragment was given a number and they were located on a map so as to keep track of their location.

The map; the numbers were indicated on the fragments with blue scotch tape.

The map; the numbers were indicated on the fragments with blue scotch tape.

Then the gluing really began, using the conservator’s favorite adhesive: Paraloid B72, diluted in acetone.

First steps of the gluing.

First steps of the gluing.

The more the jar grew, the more it needed a support, first on the outside, since its bottom is rounded….

A good support was provided by this bucket filled with glass balloons, heavy enough to stabilize the jar.

A good support was provided by this bucket filled with glass balloons, heavy enough to stabilize the jar.

…then on the inside to prevent it from collapsing on itself because of some particularly heavy fragments.

The jar was growing and needed internal support; the white material inside is a plastic bag filled with polyethylene fiber.

The jar was growing and needed internal support; the white material inside is a plastic bag filled with polyethylene fiber.

Losses in the ceramic had to be filled at the same time as the gluing to provide structural support to the jar and prevent it from collapsing.  Moreover those areas to fill would have been difficult to reach once the gluing was complete.

There was one large loss that definitely needed to be filled since one of the surrounding fragments was holding by only a few millimeters to another one.

Filling this area was a bit tricky. The fill material needed a support to be applied on the jar. Japanese tissue paper was glued inside of it and strengthened by applying several layers of Paraloid B72. It also needed to be shaped according to the curve of the jar.

On the left: The area to be filled.                        On the right: Japanese tissue paper used as a support to hold the fill material.

On the left: The area to be filled.  On the right: Japanese tissue paper used as a  support to hold the fill material.

On the left: The inside of the jar with the "tricky fragment" held in place by the japanese tissue paper.   On the right: Applying the fill material.

On the left: The inside of the jar with the “tricky fragment” held in place by the japanese tissue paper. On the right: Applying the fill material.

The fill material used is a mixture of Paraloid B72 and glass micro-balloons, looking like a very light white powder; plaster is also traditionally used to fill losses, but glass micro-balloons are lighter and don’t bring any salts to the ceramic. That kind of fill is also reversible and completely neutral towards the ceramic.

Here’s the fill once finished and polished with a heat spatula, ready to be painted.

The fill almost finished: the building can go on.

The fill almost finished: the building can go on.

More fills and building to come in a next post !

 

 

The wooden heads, paraffin and a lamp.

Example of the burial environment of two wooden Egyptian  Statues in Saqqara (from HARVEY, Wooden statues of the Old Kingdom, plate I).

Example of the burial environment of two wooden Egyptian
Statues in Saqqara (from HARVEY, Wooden statues of the Old Kingdom, plate I).

The cleaning of the two heads is now in progress, and almost finished on the head with the wig.

But first, let’s talk about the main problem concerning those heads: paraffin. Thanks to W.M. Flinders Petrie’s publication about his preservation practices in the field (PETRIE, Methods and aims in archaeology), we knew in advance what to expect. He wrote that he used paraffin wax, almost at its melting point, to impregnate wooden objects that were very damaged. Using paraffin for that purpose, and on many other materials, was very common from the 19th to the first decades of the 20th century. Thanks to it we have artifacts instead of wood powder, which nevertheless presents some issues !

As far as we know, the heads were found very decayed and couldn’t be lifted from the ground. To facilitate their removal, the paraffin was spread on them while still half buried. That explains the current condition of the surface: here the paraffin takes several shapes.

White deposits (seen in photos below) on the surface are due to an application of paraffin in a non-optimal? environment. Indeed, the paraffin is brought to its boiling point and is supposed to remain warm enough to flow far inside the porous material. If it doesn’t, you might obtain something like this :

White deposits on the surface, due to the precipitation of paraffin applied in the field.

White deposits on the surface, due to the precipitation of paraffin applied in the field (magnification x10 and x25).

 

Those deposits cover the eyelids and the polychromy too (magnification x12,5  and x50).

Those deposits cover the eyelids and the polychromy too (magnification x12,5 and x50).
On the left: Yes, this yellowish tube-shaped material is paraffin !

 

More paraffin, covering the red polychromy on E17910 (magnification x25 and x20).

More paraffin, covering the red polychromy on E17910 (magnification x25 and x20).

And here is what the surface looks like:

Detailed view of the surface, similar on both heads (magnification x12,5 and x50)

Detailed view of the surface, similar on both heads (magnification x12,5 and x50).

Sediment (sand, quartz), and some vegetal particles, were stuck to the surface and it has never been cleaned since the discovery in 1898. The general texture can be described with a single word: waxy ! The paraffin was spread on the entire object, including the surrounding sediment. That’s why we have so much sand, quartz and organic elements included in the paraffin layer. That is particularly a problem for a conservator because the layers on an object generally have different textures that help us understanding the general stratigraphy. It also helps to guide the cleaning.

Several methods of cleaning were possible, all involving mechanical work, with a scalpel and requiring many hours of work ! The subtle aspect of this treatment is that we don’t want to completely remove the paraffin because it seems to hold what remains of the wood together. It’s like a shell of paraffin and inside is the wood, its cells completely disorganized as the CT-scan helps to figure out.

CT-scan picture of E17911, showing the damaged structure of the wood.

CT-scan picture of E17911, showing the damaged structure of the wood.

Here is what wood is supposed to look like when well-preserved:

Example of the CT-scan of a Japanese wooden statue from the 18th century CE, conserved at the Field Museum, Chicago. The wood growth rings are clearly visible and the structure appears to be in very good condition.

Example of the CT-scan of a Japanese wooden statue from the 18th century CE, conserved at the Field Museum, Chicago.
The wood growth rings are clearly visible and the structure appears to be in very good condition.

So, removing the paraffin would be both dangerous for the object and impossible. It was decided to remove, as far as possible, the layer that prevents us from knowing what the real condition of the object is. And it certainly hides more polychromy, especially on the head E17911. Cleaning tests indicated that in addition to mechanical cleaning, other cleaning methods are needed to reduce the paraffin on the surface.

First possibility: solvents. After trying several, it appeared that it wasn’t the best solution because this method was slow, not so efficient and penetration of the solvent into the material can’t be controlled.

Second possibility: heat. This More precisely a lamp with a bulb that provides warmth. Once warm, the paraffin melts and is much easier to remove mechanically. However cleaning the polychromy has to be carried out when the object is “cool” because of its fragility. This is the cleaning method that was ultimately chosen.

General view of the heating process.

General view of the heating process.

And many things were hidden under that waxy layer…

Cleaning the jar

Detail of the black inscription covering the jar.

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.

Image showing cleaning tests on a fragment of the jar.

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

Test 4: Ethanolethanol

Test 5: Wishab eraser.wishab

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.

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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.

Fragment before cleaning.

The same fragment after 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 before cleaning.

view after step1

General view of the fragments after cleaning.

Next step: de-gluing the fragments !

 

The heads in color.

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 E17911 – To show the remaining polychromy on the heads, the colors were enhanced using Adobe Illustrator.

Mapping of E17910 red paint layer.

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).

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:

stratiThe 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:New PictureA 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.

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.

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 19th 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.

Ch-ch-changes (In the Artifact Lab)

Visitors to the Artifact Lab these days will see a slightly different scene.

A variety of Native American objects currently in the Artifact Lab, including a war bonnet, baskets, a harpoon, a beaded vest and a wooden helmet.

A variety of Native American objects currently in the Artifact Lab, including a war bonnet, baskets, a harpoon, a beaded vest and a wooden helmet.

Rockwell Project Conservator Molly Gleeson will be on leave for the next few months, spending time at home with her baby daughter. While she’s away, our intern Laura Galicier will continue to work on Egyptian artifacts such as the wooden heads or the demotic jar. But she’ll be joined by other members of the Penn Museum Conservation team, who will be working on a variety of projects. Because of various upcoming deadlines, a lot of what you’ll see worked on will be Native American artifacts from Penn Museum’s collections.

Penn Museum Conservation intern Alexis North, working on moccasins for the Native American Voices Exhibition.  Photo by Steven Minicola, University Communications

Penn Museum Conservation intern Alexis North, working on moccasins for the Native American Voices Exhibition.

In addition to Native American Voices, our new exhibition opening March 1, 2014, we will be loaning Native American objects to exhibitions at three other museums in the new year: the Quai Branly Museum in Paris, France; the Autry National Center of the American West in Los Angeles; and at Penn’s own Arthur Ross Gallery. At other times you may see a conservator working on material from ancient Cyprus or material from the Museum’s excavations at Ur. Whenever you come, there’s sure to be something interesting to see and our conservators will be happy to talk to you about whatever they’re doing or whatever you’re interested in at our open window times (weekdays, 11:15 – 11:45 am and 2:00 – 2:30 pm, and weekends, 12:30 – 1:00 pm and 3:30 – 4:00 pm). And you’re always welcome to submit questions or comments via this blog. We’ll continue to post regularly on the doings of the Artifact Lab and Molly may even find some time to write in from home.

A demotic jar

A pottery workshop (from LICHTHEIM Miriam, Ancient Egyptian literature, 1973)

A pottery workshop (from LICHTHEIM Miriam, Ancient Egyptian literature, 1973)

Among the objects that an archaeological conservator treats, a very important one regarding the quantity is ceramic. Ceramic artifacts are widespread on time and many very different places; a lot of (if not all) civilizations on Earth made ceramics, so if you haven’t met one of those yet in a museum, it’s only a matter of time!

The one we have in the Artifact Lab is an Egyptian jar, from one of the past Penn Museum’s excavations on this site. Jars were used to contain fluids and are covered inside with a mixture of water and clay, to make it waterproof.

Here is a picture of the fragments before any intervention:

The jar before treatment.

This ceramic is covered with inscriptions painted in black ink (most likely a carbon ink) and the writing appears to be demotic. The Egyptian writing knew three different forms: hieroglyphic, which is the one you’re used to see on monuments; hieratic, which is a simplification of hieroglyphs, allowing the scribes to write faster for their administrative work on papyrus or pottery and rock fragments; and the demotic is a simplification of the hieratic, used from the VIIth century B.C. It is one of the writing that you can see on the Rosetta Stone.

rosetta stone

Demotic writing on the Rosetta Stone.

Detail of the black inscription covering the jar.

Detail of the black inscription covering the jar.

This black ink is water soluble, meaning that water is highly prohibited to clean the inscribed areas !

Concerning its condition, the main problem of course is that the jar is broken into about 50 fragments. It was restored in the past so it still bears remains of an old adhesive on the edges and many fragments are still glued together. Moreover, the surface and the inscription are covered with dust and need to be cleaned.

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Example of a particularly dirty fragment. The inscription is barely visible.

The next step will be to remove the old adhesive and to put the fragments together again. Eventually, we may have to fill some gaps in the ceramic, so as its handling could be easier and safer.

Those steps will be more detailed in several blogposts to come !