Open Varnished Wood?

[Black_Inky_Eyes]

So basically I varnished (Plastikote) the bottom of my Living World Eco Green Habitat and wasn't too worried about that because it would be covered by substrate. However, my recent Syrian has taken a huge liking to sand baths so I got him a wooden box with no lid (40 x 30 x 10cm) but I have Plastikoted it because obviously he'll use it as a toilet and I am preventing the urine from soaking in. The only thing I'm concerned about is the varnished wooden box is out in the open and not covered by the substrate, I know Plastikote is the safest varnish but surely it can't be 100% safe for a hamster to chew on wood with varnished applied to it. My current hamster hasn't chewed up any wooden toys or flavoured chews but he has gone crazy at the Whimzee dog chew. Also, the smell and toxin that the varnish produces can't be good either?

Think it's okay to add this varnished wooden sand bath?

NOTE: The varnish I use is the PlastKote B47W 59ml Enamel Paint Bottle-Creme De La Creme

Thank you!