Has anyone here any experience with overcoating cyanotype? A recent thread in another part of APUG about photo postcards got me thinking about cyanotype postcards, which I've heard of -- but I'd be concerned about postal abuses damaging the image, not to mention having to spend a lot of hours explaining cyanotype to the USPS inspectors if they happen to connect the beautiful image with the scary-named chemicals that are used to make it (to the ignorant, any chemical with "cyanide" in the name must be terrifically toxic, right?). Overcoating the image would help in both senses, by protecting it from liquid splashes, alkali in the environment, rubbing off the paper, and so forth, as well as "protecting" postal personnel from contact the the "hazardous" Prussian Blue pigment... Question is, what overcoat works? Artist's fixative spray, in my experience with drawings when in high school and college, isn't all that great (and neither is Aquanet hair spray, though it's both better and cheaper than fixative), and I have no idea what they'd do to a cyanotype (though that part's easy enough to find out). What about a brushed or air sprayed coating, either a lacquer of some sort (model airplane butyrate dope, say) or a urethane product (like thinned Varathane varnish), or even shellac? Gelatin, albumen, or starch? Something else I'm not thinking of?