Dye ink prints: behind glass vs ???

Started Oct 23, 2012 | Discussions thread
Mark McCormick Senior Member • Posts: 1,176
Re: Dye ink prints: behind glass vs ???

Zone8 wrote:

JulesJ wrote:

We put everything behind glass. But something no one has mentioned is that you should not have the print touching the glass. You either have to have a box frame, or use a mount/matt thick enough to space the print away from touching the glass, otherwise it could stick over time and look awful as well as damaging the print.

However, as Jules said, glass contact can glaze the surface of all photo-type papers (mostly plastic these days but would include traditional silver-gelatin prints or inkjet prints with a baryta base) leaving the surface firmly attached to the glass, so the gap is essential. In addition, glass contains acids.

Modern soda lime glass used for picture frame glazing is comprised of silica, alkali (sodium), and earth alkaline oxides. Glass corrosion involves leaching of the sodium to the surface of the glass, then mixing with water to form sodium hydroxide. Soda lime glass is therefore not acidic nor are the leached products of its corrosion process, but glass does indeed corrode under high humidity conditions. We are only talking about angstroms of depleted sodium coming to the surface over very long periods of time (decades), but eventually that corroded interface wouldn't be an ideal surface to be in contact with photos, either. All that said, the preservation problems of modern glass corrosion is really no bigger than the problems posed by an air gap for many modern media.

The concerns about photos eventually sticking to the glass when in direct contact stem not from the glass but from the gelatin layers of traditional photos. Gelatin reverts from hard dry polymer to a gel state under high humidity conditions (i.e., it crosses what scientists call it's glass transition temperature at about 75% relative humidity at normal room temperatures). Not all modern inkjet media have binders that will do this, so some are safe when in contact with glass, but that said, if you're not sure whether the media you've chosen can tolerate contact with glass or not, you might as well play it safe and leave a gap as others have recommended.

kind regards,


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