IMO you can forget the idea of using painted plywood for building your fume hood
Painted plywood just will not hold up - the corrosive chemicals we work with are going to get under the paint & cause the paint to peel away from the plywood --- just like the chems we use to recover gold foils from gold plated fingers/pins get under gold plating to relieve gold plating from base metal those chems get under paint & cause the paint to start peeling
Depending on how much chem work you do in your hood the fumes from reactions will cause the paint to start peeling from the walls & ceiling of the fume hood within a year or two - spills on the floor of the hood will cause the paint to start peeling in even less time - like plus/minus 6 months
And for what it is worth - any reactions with nitric acid will cause the wood fibers in the plywood to turn in to "gun cotton" once the paint starts peeling - gun cotton is VERY flammable meaning your hood is going to become a fire hazard in your lab once the paint starts peeling &/or nitric spills get under the paint on the floor of the hood
Use the plywood you bought to build something else - then go to the lumber yard & buy melamine to build your fume hood out of
Melamine is incredibly hard &
very acid resistant - it is also very smooth & so is very easy for wiping up spills
In this thread you will see pics of the fume hood I built out of melamine
https://goldrefiningforum.com/threads/building-a-chemical-fume-hood-with-a-plain-steel-blower.23107/
I used that hood
everyday for 10 years & other then stains on the floor of the hood from spills the hood was as good as the day I built it
To put that in perspective for 10 years my hood ran 24 hours a day 7 days a week - the one & ONLY time I shut that hood down was for a couple days to up grade the venting system with bigger vent pipe & bigger blower
Go buy melamine to build your hood - use the plywood you bought to build something else
Melamine will last MUCH longer & your hood wont become a fire hazard like painted plywood will
Here is a like to melamine at Home Depot - make sure to get the double sided melamine & not the single sided melamine
https://www.homedepot.com/p/Melamin...ickid=VpVXxXSk1xyPTmowC70DE3uXUkHRA5XIr1bTSc0
Kurt