Paraloid B 72

Paraloid B 72 has been used since the 1950s in conservation as a consolidation agent and as a picture varnish.
Extended tests have shown it to be one of the most stable resins used in the conservation of works of art.

Base
Copolymer of ethyl methacrylate.

Available
100% Granulate
  50% Solution in Toluene
  40% Solution in Acetone
  15% Solution in Ethyl acetate
other costum concentrations are possible
Fixative Spray 15% in Ethyl acetate


Applications

Paraloid B 72 is used to consolidate and impregnate mural paintings and oil paintings, as a fixative for charcoal and chalk drawings, pastels, as well as for the consolidation of wood. It is also recommended as an adhesive for glass and ceramics.

   

Properties
• thermoplastic acrylic resin
• lightproof and age-resistant, non-crosslinking
• medium-hard
• glass transition temperature, approx. 40°C
• softening point, approx. 70°C
• melting point, approx. 150°C

Solubility
Soluble in toluene and acetone. Dilutable with xylene,Shellsol A, isopropanol, ethanol, methoxypropanol(PM). Insoluble in White Spirit.

Viscosity
approx. 200 mPas in acetone (40% solution at 25°C),
approx. 600 mPas in toluene (40% solution at 25°C),
approx. 980 mPas in xoluene (40% solution at 25°C)

Application
When working with Paraloid B 72, the right thinning rate is decisive for a successful treatment. Tests should be made in order to determine the thinning rate and the appropriate solvent to provide good penetration and consolidation properties. Since objects show different absorptions, it is advisable to work with lower concentrations and, if necessary, to repeat the application.
There is a risk of undesired saturation on the surface of the object when working with too high concentrations.The solvent retention must be taken into consideration.
Especially when using solvents with a low evaporation rate. It may take days or weeks for complete evaporation of the solvent. The result of the consolidation can be judged only after complete drying of the resin. Excess resin or gloss are to be removed with toluene.

Examples

a) Mural paintings
For the consolidation and impregnation of mural paintings (a fresco/secco), limewash and silicate paint,crumbling plaster, etc. a solution of max. 5% in toluene/isopropanol is used. lt is applied in several layers until the required degree of saturation is reached.

b) Paintings
For the conservation and consolidation of ground and pigment layers on wood or canvas supports, a 5 - 10% solution in toluene or toluene/isopropanol is to be used. After drying, possible cuppings can be flattend out with a heating spatula.
When used as a varnish, a 10% solution in toluene/xylene is applied. While the first layer can be applied with a brush, each subsequent layer should be sprayed on.
Please note that in certain cases, depending on the ambient temperature, hazing can occur due to evaporation.To overcome this problem, 10% Shellsol A or methoxypropanol (PM) should be added to the spray solution.

c) Wood
For wood consolidation, solutions of 5 - 10% in Toluene are recommended. Impregnation is to be done in a wet-in-wet technique until saturation is reached. For slower and deeper penetration, solutions in toluene/xylene or toluene/ Shellsol A are preferable.

d) Glass and ceramics
Paraloid B 72 has proven useful as an adhesive for glass and ceramics. Solutions in acetone, acetone/alcohol dry very quickly. Depending on the porosity of the fragments, the edges should be isolated with a 10% solution to ensure good adhesion. A 20 - 40% solution is to be applied along the edges before the fragments are put together. Another method consists of reactivating the dry adhesive with solvent before the fragments are joined.

e) Application as fixative
Paraloid B 72 is also very suitable as a fixative for pencil, chalk and charcoal drawings, pastels, etc.
Spray applications of 2 - 4% in toluene/isopropanol are recommended. 



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