Homemade fixative for chalk pastel
Here are some additional recipes to complement fixer1234's extensive answer:


The easiest and most likely candidate for a homemade fixative is milk.
Van Gogh protected a lot of his drawings using regular milk (and water)1 - at times pouring out entire glasses over them. The reason he opted for milk was because he wanted to get rid of the sheen of charcoal and graphite.
If you happen to have any casein lying around, a casein fixative might be a good alternative.
Mix casein with (grain) alcohol and (distilled) water, in a 1:2:5 ratio.2
See here for more experiences (and likely some troubleshooting).
And in case you have any shellac at home, you can try mixing it with isopropyl alcohol in a 1:4 ratio to create a shellac fixative3, which you can apply using a spray can.





1: http://vangoghletters.org/vg/terminology.html, see under 'fixing'
2: https://dbclemons.wordpress.com/2016/10/27/homemade-casein-fixative/
3: https://www.ehow.com/info_12066271_homemade-fixate-charcoal-drawing.html