Tag Archives: powdery leather

Stabilization is fundamental

Sadly, leather afflicted with red rot can never be brought back to its original healthy state again. The weakening and embrittlement are irreversible. All the more, it is essential to consolidate the powdery leather to strengthen it before undertaking any tear repairs, otherwise the repairs simply won’t hold and the leather will crumble apart. Our solution to the problem is described below.

Consolidation: For the trim leather, I found it best to use a combination of consolidants, taking advantage of each of their favorable properties.  Not having enough Pliantex to treat all four panels, I am reserving it for the cracks and splits in the varnished main sections of leather that are sensitive to alcohol.

The following system evolved from my mock-up trials for consolidating the trim, and is working really well so far: I brush-apply (fairly liberally) two consecutive coats of 1% Klucel in ethanol—it easily penetrates and almost immediately disappears into the leather; this is followed by an application of 2% Klucel; and finally, an application of the Klucel/SC6000 mix (equal parts of SC6000, 2% Klucel in ethanol, and ethanol) which mostly seems to sit on the surface and seal it. The latter adds strength, seals the surface, and dries to a nice sheen that is in keeping with the original finish. To get the solution underneath the lifted bits and edges of the trim, a small syringe works better than a brush.

For the main painted/varnished areas, Pliantex will be used exclusively, as it is the only material that seems to work (hoping that we don’t run out before the end of the project).

Keep in mind that all of this is just part of the preparation for lining tears and securing loose bits of the fragmentary trim. Without consolidation, it would be impossible to adhere anything to the powdery leather, since it would just flake or peel off almost immediately.

Incidentally, I did some preliminary tests on a scrap piece of leather (flesh side) consolidated with various dilute adhesives, then adhered strips of non-woven polyester to it with BEVA 371 film by heat-setting. When I qualitatively tested the peel strength of the Beva/fabric, I was surprised that the leather fibers broke and gave way on all the samples except for Pliantex. The strip was nearly impossible to peel off the sample consolidated with Pliantex since the leather fibers would not break. This tells me that it’s superior in strength to the other agents of consolidation commonly used for powdery leather.

Here is what an area of the border looks like after consolidation. The color of the leather has darkened somewhat due to saturation, which is inevitable, but it has gained significantly in strength and flexibility.

Compare to the same area before consolidation.

By the way, does anyone know why Pliantex was discontinued? If someone has found a source or reasonably good substitute for Pliantex, please, please let me know!

I will be adding more info as the treatment progresses. Next up will be reinforcing the  loose fragments along the edges, and then later on I’ll discuss the process of lining tears and splits.

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Reflections on powdery leather

Developing a treatment plan: The main challenge has been finding the right consolidant, one that will improve the leather’s strength so subsequent repairs will hold. I have plenty of experience working on leather artifacts, and know what the limited options are when the leather is this degraded. Klucel G works well in the short-term (it has good penetration and effectively consolidates the powdery surface) but is relatively weak, and is known to have a short lifespan of usefulness. What’s more, Klucel is fairly brittle and has shown unsatisfactory long-term ageing characteristics, particularly in an acidic environment such as that encountered with deteriorated leather (e.g. in the presence of sulfuric acid from absorption of sulfur dioxide in the atmosphere).

I recently began using Klucel/SC6000 mixture with good results in terms of improved strength and flexibility; the problem is that it tends to sit on the surface and does not penetrate into the leather structure very well. I’ve also used Pliantex in the past with a very good outcome. Despite the nasty smell of the solvents, it has excellent penetration and imparts sufficient strength and improved flexibility to the leather. Unfortunately, this product has been discontinued and is no longer available!  (We happen to have a small supply left over from a similar treatment we did some years back–possibly just enough to last through this project.)

This is a dilemma we all struggle with at some point in our careers as conservators. It is understood that any consolidant introduced into a porous material such as leather, is for all intents and purposes, not reversible. It would be nearly impossible to extract the consolidating agent from the porous material completely. And why would you ever want to, as long the material is stable and is not causing any harm or threatening the future stability of the object in question? There are really only two choices: 1) either to do nothing at all and let the object continue down the path of deterioration and eventually cease to exist, or 2) do something that we’ve been taught to avoid, something that defies our ethical sensibilities—that is, something not readily reversible—and by this intervention, ultimately allow the object  to survive for future generations to enjoy.

A description of the actual treatment (so far) is coming soon…


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The challenges of working with degraded, powdery leather—Four panels from a painted leather screen

A bit of background on the panels: in another life they formed a screen, but it appears the leather was cut from something originally larger (possibly wall paneling in a room, or an even larger screen). This is suggested by the sharp cut lines along the edges and the fact that part of the painted/embossed border design has been trimmed. The wood frames to which they are now attached appear to be relatively recent. Narrow strips of leather secured with brass nails were added to cover up the cut edges.

Each of the four panels is comprised of  two sections of leather stretched over a wooden  frame. The leather is embossed and painted with floral and animal/bird motifs. The surface is varnished overall and stained to give the painted background an “antiqued” appearance.

Current condition: The leather is extremely desiccated and brittle, and shows an advanced stage of a type of deterioration known as red rot. The latter includes overall loss of strength, embrittlement, desiccation, and associated cracking, flaking, and powdering of the leather with resulting breakage and loss of fibers—this is particularly apparent in the leather trim along the edges.

This is what red rot looks like up close:

You can see that the fibers are breaking up and crumbling to dust.

The problem, simply stated, is that the leather is disintegrating. The fibrous structure made up by the collagen protein is literally breaking apart and turning into dust, especially in the trim leather, which is of a different type than the large pictorial areas. The trim is extremely ragged in appearance due to the abundance of losses. There are a number of tears and splits in the primary decorative leather as well, the worst of which is across the bottom of  panel #1 (below). To complicate matters, the varnish on the main leather (but not the trim) is sensitive to many solvents, including alcohols; it is not adversely affected by naphtha or xylene.

A comprehensive discussion of the mechanisms of leather deterioration can be found in Conservation of Leather and Related Materials by Marion Kite and Roy Thomson. I highly recommend this book for anyone that is working with leather.

Oh, I should mention that the backs of the panels have been lined with a layer of acidic paper and a heavy woven cotton fabric. Both are adhered with animal glue! Ugh!! Oddly enough, the fabric does not extend all the way to the edges of the frame, and looks as though it was applied after the leather was stretched onto the frame! Not a well thought-out solution, and clearly not the work of a professional conservator, nor even that of a skilled restorer.

Removing the lining is not really an option because the leather is too weak and the damage this process would likely cause is too great (plus, our dear client has limited funds). Therefore, we will only be removing certain sections, where it’s necessary to gain access to the back for mending tears and splits.


Coming up next:  Treatment highlights

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