Photo / painting on curved glass
Posted: Sun 08 Nov, 2009 11:47 pm
A regular customer has brought in a unusual item where the image is on the reverse off a piece of curved glass. I have never seen one of these before, but I believe I have pretty good instincts when figuring out what most things are. In this case, I believe this to be an early type of sepia photographic print, (possibily later Victorian era), which has been painted from behind so that the painted on colours show through the non-opaque areas in the image. I have no concerns about the condition of this item and consider it safe for re-framing in it's repaired, original frame.
When it arrived, there was a piece of old and well browned (no doubt acidic) pulpboard on the back which had been taped in place using an early type of black tape, (Victorian photo album tape?), taped around the front of the glass and onto the rear of the pulpboard.
I have already removed and discarded both the pulpboard and the tape, which I must now replace. My assumption is that there may or will be photo-chemical activity / compatiblity issues concerning what I use to replace the afore mention discarded materials.
My best guess is that the rear of the photo is painted with an egg albumin based paint and perhaps the photographic medium would also be egg albumin based. For this reason, I am not entirely happy about using an archivally safe tape with a water based adhesive, in case any moisture may be transfered to the suspected egg albumin based materials. However I am even more concerned about using anything which includes any self adhesive materials, due to chemical compatiblity or out gassing contamination issues.
I am current thinking that I will use the archival tape whic includes a water activated starch based adhesive and will check that all the water has been fully absorbed into the paste, before taking care to ensure that the tape cannot come into contact with the any materials on the rear of the glass. I am also thinking that I will replace the discarded pulpboard with a cottom rag museum mountboard.
I have found it very hard to find any specific guidance in any of my reference books or elsewhere. An experienced conservator I know also agrees with my thinking and believes that I am intending to do all the right things, but she has never encountered anything like this either.
Beside welcoming any additional advice, I thought this would be a potentially informative subject for discussion and exploring relevent issues.
When it arrived, there was a piece of old and well browned (no doubt acidic) pulpboard on the back which had been taped in place using an early type of black tape, (Victorian photo album tape?), taped around the front of the glass and onto the rear of the pulpboard.
I have already removed and discarded both the pulpboard and the tape, which I must now replace. My assumption is that there may or will be photo-chemical activity / compatiblity issues concerning what I use to replace the afore mention discarded materials.
My best guess is that the rear of the photo is painted with an egg albumin based paint and perhaps the photographic medium would also be egg albumin based. For this reason, I am not entirely happy about using an archivally safe tape with a water based adhesive, in case any moisture may be transfered to the suspected egg albumin based materials. However I am even more concerned about using anything which includes any self adhesive materials, due to chemical compatiblity or out gassing contamination issues.
I am current thinking that I will use the archival tape whic includes a water activated starch based adhesive and will check that all the water has been fully absorbed into the paste, before taking care to ensure that the tape cannot come into contact with the any materials on the rear of the glass. I am also thinking that I will replace the discarded pulpboard with a cottom rag museum mountboard.
I have found it very hard to find any specific guidance in any of my reference books or elsewhere. An experienced conservator I know also agrees with my thinking and believes that I am intending to do all the right things, but she has never encountered anything like this either.
Beside welcoming any additional advice, I thought this would be a potentially informative subject for discussion and exploring relevent issues.