MITRA Forum Question Details

Every organic coating will yellow to some degree. Some like most Regalrez yellow so little that it is imperceptible. Others like most acrylic dispersion mediums yellow minimally so that it is not noticeable unless the layer is applied quite thickly. Oil mediums tend to yellow more than this although some of the oil modified alkyds are better in this regard. So yes, there will be a little yellowing but as the layer is very thin, this may not be disfiguring.

As to adherence, drying oils are poor adhesives unlike acrylic and PVA dispersions which are very good adhesives. The alkyd component in your medium would improve its performance but not to the degree as those two. Probably, if you find that the glitter is well adhered, it will remain so, but I cannot say so with authority.

Others may have a more concrete opinion on this.

Artists' alkyd mediums are usually quite long, meaning that they contain a good deal of drying oil as well as the modified alkyd resin. The reason we caution against having them as a surface coating is precisely because they will yellow to some extent AND they are not irreversible (at least they could not be reversed in anything that would not harm the original painting).

They probably would not harm the paint beyond this with the possible exception that they tend to be formulated to dry quite quickly. I can envision a circumstance where the alkyd is applied too soon after the oil paint creating the situation where the surface layers dry but those under are still soft. You could easily avoid this be waiting before applying the alkyd (the appropriate period of time would correlate to the thickness and composition of the lower oil paint layers).  

To reiterate, the primary issue here is the potential yellowing and irreversibility.