There were kits sold in the 1960's & 70's for tinting glass @ home "hobby/crafts-styled product... during this same time period , an automotive line of funky liquid 'window-tint' , in several colors including green & pink .
A number of amber & green light fixtures (mostly imports & 'swags') were sold & seen around town - they were cheaply tinted , during 'Harvest Gold-toned' appliance times .
Earlier items were seen , that mimicked fancy & expensive stained-glass lamps (at a shortish distance) .
Some folks in the 1910's - 40's were known to shellac or laquer their stained glass lampshades .
Dye & paint-washed glass has been known in europe for centuries , primarily in building use (windows) .
I tend to think of most any cold-applied colored liquid that is coating glass surfaces as 'tint' .... horseshoes , handgrendades & tint ...close enough for me ....
Other coatings have their own properties & methods of application , including fusing , sprays and bondings & so on .
The history of adding mat'ls to the surface of glass , in order to tint it , is a big one .
My speculation on it's origin would be that the original piece was probably fused sand from a campfire with a drop of blood on it .
One thing that will stain glass for good is analine dye (speaking of toxic stuff!!) .
Sometimes , if a flat-glass item is old enough , you can get a fair guess of it's age - due to the fact that glass is a liquid , it will flow at a predictble rate (& it's thickness can be easily measured with a caliper) .
It's really a good idea to check the thickness of older flat stained & leaded glass .... & hang (and transport)the 'thick' edge pointing down ...doing so can/will prevent thinner glass from fracturing , esp from frame pressure .
The down side of hanging some very old 'stained glass' is that sometimes you find out that it was not hung in the way you want to display it ... bottom line on that is : check it before you buy it .
Oop ! Looks like I've hijacked again , ironlord - BTW , good eyes & great question !
