Glass required?

[pramsay13]

Whenever I get an oil painting on canvas or board I check if the customer is looking to have glass in the frame.
This time I have oil on card so wondering if it's okay to frame without glass. The whole card has been covered with oil paints.

[prospero]

This is usually fine. Prepared canvas boards (grey board wrapped in canvas) are OK to a point although they are
more suitable for preliminary sketches than 'finished work'. Smaller ones are no problem generally. Bigger sizes can
bow and sometimes need fixing to an extra board give them more substance. Paintings on wood panels (ply or MDF) are OK
if the surface has been primed properly.

Some folks think it's a good idea to use oil paints on bits of card or even paper. A surface for oils needs careful prep. Raw
paper or card will soak up the oil and generally no work as it should.

In most cases the use of glass is down to personal preference. Ones that are painted on iffy substrates maybe do need extra protection.
Ones that are done 'proper' can take any manner of insult and still be repaired satisfactorily. One on a cornflake packet that gets
jabbed and torn is harder or impossible to restore.
Oil paintings have a certain presence and generally are quite bullet proof. Using glass can be akin to chewing a toffee with the paper on.
If glass must be used for whatever reason then AR glass is the thing. UV protection isn't really necessary in my exp. Never seen a faded oil painting.

Another thing to think about is that oils take a while to fully dry. they don't so much dry as cure. This can take decades. Sealing
a fresh painting against the atmos creates a micro climate which will interfere with the natural curing process. Whatever people
tell you, oil paintings do need to breathe.

[Jamesnkr]

For oils on paper, the paper needs careful treatment else it suffers.

[JFeig]

Prospero,
I think you mean that oil paintings need oxygen to oxidize the oils in order to cure. This is like steel rusts.

Due to the nature of the substrate of the painting I would suggest glazing the item. Oxygen will pass through to the painting from the back and unsealed edges.

[Steve N]

just make sure you use spacers or a mount