7 7. CONCLUSIONS

This study describes the physical and working properties of cyclododecane and also addresses the issues of penetration and rate of sublimation from porous stone substrates. Both the amount of cyclododecane delivered to a substrate and the depth to which the consolidant penetrates are variable with application method, whether delivered as a melt or as a saturated solvent solution. The concentration of saturated solutions differs depending on the solvent used, thus varying the amount of consolidant applied to the substrate. The size of consolidant crystals and the compactness of the cyclododecane coating also varies with delivery method. Solvent solutions carried the consolidant into substrate pores, while melted cyclododecane did not readily penetrate unheated porous substrates. Sublimation rates differed for the various delivery methods. More time was needed for the solvent-delivered consolidant to sublime from within a porous substrate than for the melted coating to depart from the surface, regardless of the amount of consolidant applied. It should be noted that, although not part of the present study, the introduction of an additional factor, such as heating of the substrate, may greatly increase both the penetration depth and the subsequent sublimation rate from pore structures. Sublimation rates also differed for the two stone types evaluated, suggesting that substrate properties such as porosity, pore size, permeability, and mineralogy affect consolidant loss. The presence of salts, soiling layers, and materials introduced in previous treatments may also influence the penetration and sublimation rate of cyclododecane applied to porous substrates.

Provided adequate time, cyclododecane did depart from stone substrates without leaving residues detectable visually, by weight, or by GC-MS. A more direct method of assessing the extent of sublimation might be desirable when developing protocols for the practical use of cyclododecane, especially when further treatment is needed after sublimation of the temporary consolidant. Determining the amount of time necessary for complete sublimation will require testing for each substrate and delivery method. If treatments with cyclododecane are to be followed by additional treatments, it may be advisable to use application methods that promote only limited penetration, allow plenty of time for sublimation, or encourage sublimation by increasing ambient temperature or air circulation.