Printing > Print Outgassing

The water used in pigments and dyes evaporates quickly.

Glycol, a humectant, evaporates slowly from glossy and semi-glossy papers (RC papers).

Glycol is beneficial because it slows the evaporation of the ink, preventing nozzle clogs.

However, if a print is framed immediately after printing, the slowly evaporating glycol may collect on the glass as an oily fog.

This outgassing occurs with glossy and semi-glossy papers because there's an impervious polyethylene layer between the paper base and the ink accepting layer on top.

Because of this barrier, the paper base is unable to absorb the glycol, which would speed its evaporation.

Prints must be allowed to dry completely.

After the print appears to be dry, interleave it with sheets of watercolor paper.

Some photographers coat their prints with sprays, such as Lyson Print Guard.

However, without research, this writer wonders if sealing in the glycol can affect print and color stability.

Here's an article from Epson about the issue.

Framing Tips for Photographic Papers (PDF)