1907.] OR Conservation of Historic Buildings and Frescoes. 601 



Thus far I have spoken about our chief agent of destruction, 

 sulphuric acid, describing its sources and connecting it with stone- 

 work on the one hand and with certain mural paintings on the other. 

 Xow I purpose deahng with certain preservative and restorative 

 methods, taking, in the first place, stone-work into consideration, then 

 mural paintings. My aim will be to describe two methods of treat- 

 ment only — methods which are not always available, though of wide 

 application. 



In reference to decayed stone-work, I would name the opening 

 section, " Baryta versus Lime." Some persons interested in the pre- 

 servation of old buildings, and rightly refusing the ignominy of a 

 coat of common oil-paint or of prosaic cement, recommend treating 

 the decayed and decaying stone with lime-wash (not whitewash). 

 The suggestion is an obvious one, l^ut unfortunately this easy process 

 is unsound in theory and ineffective in practice. Moreover, the 

 application of this meagre and indiscriminate lime-wash destroys all 

 the exquisite qualities of tone, colour, texture, and translucency 

 which old stone- work may still possess in its age-worn state. And it 

 cannot fail to distort and even obliterate the last surviving traces of 

 surface-enrichment, of mouldings and carvings (e.g. the decaying 

 diaper-work in the spandrils of the great arches in Westminster 

 Abt)ey). Lime forms a crust on the decayed stone ; lime does 

 nothing towards the consolidation of the disintegrated substance ; 

 hme is itself subject to the same chemical changes which have injured 

 the stone ; lime sooner or later falls off, bringing with it the decayed 

 layer to which it was applied. Mr. Thackeray Turner, one of the 

 most strenuous apostles of the gospel of lime-wash, cited {The Times, 

 Xov. 19u4) the case of lime-washed cottages in Wales and Cornwall 

 as evidence of the preservative value of this treatment. But as we 

 are dealing with urban, not rural conditions, such evidence is beside 

 the mark. Baryta, it is true, is a late-comer compared with lime, but 

 it has been used, though in a half-hearted way, for forty-five years. 

 Had it been known earlier to the advocates of lime, it ought to have 

 ousted that earth ere now. Having the choice of two earths, why 

 not use the better ? Please visit the eastern walk of Westminster 

 Cloister, and look at what has just been done to the ribs and vault of 

 the bay nearest to the Abbey : no London dirt can turn that prose 

 into poetry. 



Let me describe the theory and practice of the baryta treatment of 

 decayed stone. Baryta-water only is used, the liquid being applied, 

 when all dust has been l)lown away, in the form of extremely fine 

 spray, on very tender surfaces. Where the stone will bear it a rose 

 syringe or even a l)rush may be used. Indeed, after a few sprayings 

 and the lapse of a week or two, it is generally feasible to adopt the 

 rougher methods. The rationale of the action of baryta is simple. 

 The liquid, which saturated at 16" C. contains about 8 per cent. 

 of BaO, is absorbed by the decayed stone^ penetrating to some 



