Yes, it is possible to apply varnish on a sheet that is already lithographed and has a final varnish. However, it is important to consider a few factors before doing so:

1. Make sure that the additional varnish is compatible with the existing final varnish. There may be problems of adhesion or chemical incompatibility if the coatings are not compatible with each other.
2. Note that adding an additional layer of varnish may affect the properties of the film, such as its flexibility and wear resistance. This may be relevant in subsequent manufacturing stages, such as flanging and cordoning.
3. Ensure that the curing process of the additional varnish is adequate and does not adversely affect the quality of the existing lithography or the integrity of the original final varnish.

If you are considering applying additional varnish over an already lithographed sheet, it is advisable to consult with an expert in the field or with the varnish supplier to ensure that the process is adequate and does not cause problems in the quality of the final product.

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