Faraday to William Francis Cowper   21 May 1860

Royal Institution | 21 May 60

Dear Sir

Your letter of the 19th¹ contained two questions on which you do me the honor to ask my opinion viz whether the damp that may be included in the stone and covered by Mr Szerelemy’s process being prevented from escaping by the surface may not ultimately lead to decay? and whether his process is in effect superior to the application of a coat of paint?² Being told that Mr Szerelmey’s process included first the application of a silicaferous operation & then the application of a bituminous coat, I enquired and was informed that the latter was to be applied when the stone was perfectly dry. If their intention be properly carried out I do not think that any bad result dependent upon moisture left in the stone will occur.

Whether Mr Szerelmey’s process is at all superior to the careful application of a coat of paint is a question I must remit to those who have had experience of the value of the latter protection. I have not had that experience & as I have said before³ the experience we have had of Mr Szerelmey’s process or Mr Ransome’s process is by no means sufficient to establish with certainty the protecting power for many years of either one or the other or shews the superiority of one over the other. Nevertheless as you did me the honor to ask for the best opinion I could form under the cir[cumstan]ces I felt bound to respond to your wish informing you at the same time of the degree of reservation I was obliged to make & as betw[ee]n the 2 or 3 parties concerned, judging with the utmost degree of impartiality my mind was capable of. I only regret that I cannot make the evidence more forcible or my opinion stronger.

I ha - | signed M. Faraday