Reversibility of consolidation

The first super-deep drilling to 12.8 km in the Kola peninsula of Russia verified the effect of de-consolidation (the reverse of consolidation) in rocks at a depth >5 km (Dortman, 1992). This effect results from the increase of fracture content and porosity of rocks at depth. 

Due to the limited reversibility of consolidation treatments for ceramics, new consolidations are carried out only if the object is seriously endangered, e.g. when the ceramic body is crumbling or the surface decoration is flaking off the surface. Materials, such as Paraloid B72 (already mentioned for glass conservation) or silanes and siloxanes (used for stone conservation) can be applied by brush, injection, spray or by immersion. Vacuum impregnation might be useful to achieve deep penetration with the consolidant. 

Table III. Reversibility of Consolidation Treatments as Indicated by Residual...

The reversibility of consolidation treatments has been shown to be incomplete (Figure 5.6) or nearly complete (Schniewind, 1988). 

Schniewind, A. P. (1988). On the reversibility of consolidation treatments of deteriorated wood with soluble resins. In Wooden Artifacts Group Specialty SessUm, New Orleans, June 5, 1988 Papers. American Institute for Conservation. 

The structures of sol-gel-derived inorganic polymers evolve continually as products of successive hydrolysis, condensation and restructuring (reverse of Equations 1-3) reactions. Therefore, to understand structural evolution in detail, we must understand the physical and chemical mechanisms which control the sequence and pattern of these reactions during gelation, drying, and consolidation. Although it is known that gel structure is affected by many factors including catalytic conditions, solvent composition and water to alkoxide ratio (13-141, we will show that many of the observed trends can be explained on the basis of the stability of the M-O-M condensation product in its synthesis environment. 

The conclusion which can be drawn from the above studies is that the skin layer in integrally-skinned reverse osmosis membranes consists of a single layer of consolidated Sol 2 type micelles. 

Complex degradation processes generally occur to some degree, even in controlled environments. In the case of wood, such processes terminate in reversion to topsoil in the natural environment. The conservation of archaeological wood might best be defined as any effort directed toward the retention of desirable intrinsic characteristics. In other words, conservation attempts to slow down or reverse the process that turns a fauteuil into fertilizer. Consolidation is one of a number of treatments available to conservation. Before approaching the technical aspects of consolidation, it is useful to have an overview of the process and to relate its role to the field of conservation. 

Selection of the primary consolidant is based on the materials it will interact with and the method of introduction. It may be selected for high reversibility, or to isolate a less reversible secondary consolidant selected for strength enhancement, or it may be selected for its ability to integrate extremely disintegrated fabric. 

It is a matter of debate whether memories can be erased at all (Jacobs and Nadel 1985). However, there is some evidence from animal experiments that processes that lead to learning or LTP-induced changes in interneuronal communication can be reversed by specific opponents of the consolidation cascade, as for instance phosphatases (Genoux et al. 2002 Lin et al. 2003a,b). The decay of both LTP and memory seems to depend on NMDA receptors. However, there are conflicting data as to whether recurrent activation of NMDA receptors promotes decay or long-term consolidation processes (Shimizu et al. 2000 Villarreal et al. 2002). 

Electrochemistry has been used for more than a century in the treatment of ancient metal artifacts [281], Ideally, this technique should be able to reverse the corrosion processes that have progressively transformed the metal into an ionic compound. Depending on the conservation state of the artifact, priorities have to be attributed and the treatment will be different if consolidation, stabilization, or cleaning is privileged. 

Parylene-C is of potential interest in conservation because of the unique application method that can result in the formation of thin, uniform, and strong films within porous or fibrous materials. However, the polymer has the disadvantages of being a non-reversible consolidant that is sensitive to ultraviolet-induced oxidation. 

Foley AG, Murphy KJ, Hirst WD, et al. The 5-HT6 receptor antagonist SB-271046 reverses scopolamine-disrupted consolidation of a passive avoidance task and ameliorates spatial task deficits in aged rats. Neuropsychopharmacology... 

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