Consolidation treatments

In children, the intensity of the consolidation treatment is now determined not only by the child s risk classification but also by the rate of cytoreduction during induction.5 Patients who respond slowly to induction therapy (as determined by bone marrow examination early in induction) are at higher risk of relapse and are treated on more aggressive regimens. 

Domenech-Carbo MT, Domenech A, Osete L (2006) Analytical study of corrosion processes of archaeological glass from the Valencian Region (Spain) and its consolidation treatment. Microchim Acta 154 123-142. 

With relevance to the administration of thiopurines in the early course of childhood ALL, the BFM Study Group reported on the association of TPMT genotype and minimal residual disease (MRD) in 810 children with childhood ALL enrolled into their trial ALL-BFM 2000 (206). In this trial, DNA-based MRD analysis after induction and after consolidation treatment was used for risk-adapted treatment stratification. A 4-week cycle of 6-MP was applied in-between these two MRD measurements. In patients homozygous for the TPMT 1 allele or those heterozygous for a variant TPMT allele, MRD levels on treatment day 33 were equally distributed between the groups. However, when MRD levels were assessed on treatment day 78, after administration of consolidation... 

The tacit assumption in any consolidation treatment is that by improving the current value of the target property (usually tensile strength) one automatically increases the time left. However, if the half-life were affected negatively by the treatment, the opposite might be... 

There are many products and procedures for carrying out a consolidation treatment, but they all involve introducing another material into the object. As discussed above, the ideal reversible treatment does not exist. Furthermore, once the treatment is introduced it may interfere with future objectives. For example, previously buried bones in natural history collections can be very friable and have been consolidated systematically to allow their presentation. This, however, precludes that they can be dated after treatment (especially if organic resins have been used), since more carbon has been introduced in the sample. It may also, preclude analysis of DNA, or other biological molecules. 

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. 

Deterioration processes, especially caused by soluble salts interacting with moisture and microbial colonisation, will be presented in this chapter, in relation to restoration/consolidation treatments and their effects. Damage will also be considered that has occurred as a later consequence of extended ingress of moisture through damaged parts of the building or the use of unsuitable building materials. 

Stabilisation by climate control. The most desirable method to prevent damage induced by the repeated cycles of crystallisation and hydration would probably be environmental control. However, neither the selection nor the maintenance of such an ideal environment is possible if looked at realistically. Predictions of salt crystallisation and hydration from mixed salt solutions are more or less impossible, taking into account all the different parameters that influence the process. Sawdy provides a brilliant overview of the subject and considers relative humidity, temperature, air movement, type and structure of the porous support, salt mixture composition and salt concentration. It is necessary to consider not only consolidation treatments of the plaster or the paint layer, which as such may influence the transition behaviour of the salts, but also the influence of microbial extracellular slimes on the porosity of the system. 

Frequently, however, growth is not restricted to the surface. Even those microorganisms that are dependent on photosynthesis, based on carbon dioxide fixation in the light, may develop successfully just beneath the surface, e.g. in renderings and fillings. Fungi often form more or less tissue-like mycelia beneath the paint layer and have been detected in areas where casein was injected as binder for consolidation treatment of plaster (see Figure 3). 

Aspects of cleaning, as well as consolidation, have already been discussed when dealing with the barium method of extraction and consolidation. So in this section, cleaning in the context of salt extraction will not be referred to anymore. However, there are other materials that become part of the paintings over centuries of intensive use, as well as previous conservation treatments. Many of these materials were applied as a consolidation treatment. This section will therefore consider different consolidation methods before discussing how to reduce their sometimes detrimental effects. 

To summarise, bioremediated calcite precipitation as a consolidation treatment for wall paintings has not yet reached the stage of development to be recommended without more intensive tests. 

It is clear that a consolidation treatment for wall paintings suitable for all situations cannot be expected in the near future. The treatment will be determined by the amount of consolidation necessary, the material and the form of application possible at the specific site. It is also necessary to take climate into... 

If calcination is to be performed solely to feed a melter, a fine powered calcine is desired, although not suitable as such for transport or interim storage. Granulated calcine can also be fed to a ass melter, but this will be considered a calcine consolidation treatment rather than a vitrification process. 

Assimilation generally varies considerably from section to section and even between adjacent cells. The alterations of mechanical properties that occur with brown rot, loss of elasticity and axial strength, suggest that the best consolidation treatment should incorporate axial and elastic augmentation. 

Consolidation treatment of wood degraded by white rot should restore rigidity while reintegrating dissociated cells. 

Predictable set characteristics are also important to process control. Predictability of set is often a factor of application environment (humidity, temperature) and material purity. The prevalence of unstable and contaminated monomers in conservation laboratories (possibly a result of the infrequency of consolidation treatments) can be a significant problem, as incomplete polymerization and retarded transition can occur. 

Other conservation-related procedures not involving consolidation treatment were intentionally omitted from this report. 

Consolidation treatments with soluble resins can be considered reversible in principle, but it has been questioned (i, 9) whether this reversibility would ever be practically feasible. Experiments with an acrylic and a poly(vinyl butyral) consolidant showed that most of the resin could be removed from treated wood, and that the acrylic could be removed more readily than the poly (vinyl butyral) (15). In another study, a consolidation treatment of archaeological wood with Acryloid B72 in toluene could be substantially but not completely extracted again, as evidenced by scanning electron microscopic examination (22). 

Several processes take place when wood is treated with solvents. Solvents may swell wood, depending on their nature they may extract some of the adsorbed moisture some of them may be retained in wood by tenacious adsorption within and most importantly, the solvents may remove wood extractives (8). Thus, some of the extractives may be removed or redistributed within the wood during consolidation treatment, and more may be removed along with the consolidant when attempts are made at treatment reversal. It is therefore not possible to return the wood to exactly the same state as before the initial consolidation treatment. 

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. 

Hatchfield, P. B., Koestler, R. J. (1987). Scanning electron microscopic examination of archaeological wood microstructure altered by consolidation treatments. Scanning Microscopy, 7(3), 1059-1069. 

Haake, S., Simon, S., Favaro, M. (2004). The Bolc na cocktail - evaluation of consolidation treatments on monuments in France and Italy after 20 years of natural aging. In D. Kwiat-kowski, R. Lofvendahl (Eds.), Stone 2004, X International congress on the deterioration and conservation of stone, Stoddudm, 27 June-2 July, 2(X)4 Proceedings. ICOMOS Sweden, 423- 30. 

Welsh, E. C. (1980). A consolidation treatment for powdery matte paint. In Annual meeting Proceedings (pp. 141-150). American Instimte for Conservation, 8. 

We have developed different nonwoven stmctures with para-aramid fibres, and produced thick 3D stmctures by associating several nonwoven monolayers with a consolidation treatment. Porous composites were afterwards manufactured by impregnating the fibrous stmctures with an epoxy resin. Both dry and impregnated materials were characterized in terms of stmcture (density, fibre volume fraction), and compression tests were used to evaluate mechanical properties. Equivalent pore size and distance between fibre contacts were determined using theoretical models. They help to provide some insight on the mechanical behaviour of the different stmctures. 

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