varnish over chalk?

[Conrad80]

Hello all, just hoping for some advice. My friend and her now husband drew pictures of themselves some years ago on a blackboard in my kitchen. They subsequently married and had these pictures tattooed on each other. I'm going to change the kitchen soon and my plan is to give them the "original" in a frame as a gift.
My question is: how can I varnish over/ protect the chalk drawings. They will be especially vulnerable during the removal and framing process. Anyone preserved a chalk image for posterity before?

TIA for any advice xxx

I would put a piece of glass in front of it when framing rather than varnishing.

Is the blackbird a bit of plywood or part of a solid surface eg plaster? For removing it, you might spray a bit of artists' fixative to help protect the drawings but I would be cautious of varnish.

A spray on varnish might work but I would do extensive research using other chalk drawings to be absolutely sure it wasn't going to ruin it. I would not try a brush on varnish at all.

Other than that, I agree with artist fixative spray and then frame it behind glass.