Do you use a wood or metal primer on glass?

[Big Jenny]

I want to paint on glass. I have de-greased the glass, but am not sure if it's o.k. to use wood primer, or whether metal primer would be more suitable.

[heathfield]

Neither primer will do what it's designed for on glass. Just apply the paint. Note that ordinary paints on glass will eventually split and crack if they're exposed to heat, e.g. direct sunlight. Have you considered stained glass paints instead? Had them in B&Q last time I looked. These won't crack so easily, though they tend to be translucent rather than opaque.

[bricro]

I have a book "Glass painting made easy"!! A David & Charles Craft book.
Choosing the right paint:- I quote,

Glass Paint water based
Glass Paint solvent based
Porcelain Paint water based
Outliner Paste dry in about 2 days
Acryclic & Emulsion water based
Glitter Glue
Colourless Varnish

Best go to a good craft shop and talk to the owner. Good Luck