Answer (1 of 2): If you want to completely seal it then you will ruin the charcoal quality and character of the medium. If you feel you must then do it in thin layers of a light mist using a spray-on fixative. To do it otherwise you will get a very distracting and downright ugly sheen to the dark
How I Seal My Charcoal on Canvas Originals
How to Protect a Charcoal Drawing (Tips and Tricks)
Can you laminate a charcoal drawing? - Quora
Tips for Framing Pastel or Charcoal Drawings - American Frame
How to set charcoal drawing hairspray - Quora
Can you use Krylon “Matte Finish” spray as a fixative substitute for charcoal drawings? I intend to work fine details and smooth gradients, would it fix the charcoal just as good as
What are some guidelines of using fixative when drawing is complete? I tried it but charcoal getting spread when it is wet. - Quora
What to Use for Sketching on Canvas - My Sketch Journal
How to protect your graphite and charcoal artwork.
Can I use a spray varnish over a graphite pencil drawing? - Quora
How to Protect Charcoal Drawings without Fixative – The Work Buzz
Easy Tips On How To Protect Pencil Drawings Without Fixative