if you seal wood with any "good" kind of sealer, you won't have problems with anything leaking through. I used White Pine to build my rack, and my snakes are housed in Sterilite tubs. I stained and then sealed the wood. Since I have done this, the sap is not able to penetrate because the pours have been sealed. Cedar works the same way. When you buy Cedar furnature, it is sealed to protect us from getting sap on our clothes, and to protect the wood from moisture.