Denatured is just OK. The lab grade contains methanol and/or IPA (and sometimes other nasties like acetone or MEK) to make it undrinkable, un-purifiable via distillation, and hence un-taxed. It would be better to find a regent or HPLC grade where at least the extra 5% is just water. It's not that the added denaturants are necessarily harmful to records at the concentrations employed, it just that the producer doesn't always disclose what exactly they are. If they are just methanol or isopropanol, then it isn't anything to worry about. If it is some denatonium salt, then I'm not so sure I want to experiment with it. That said, I'm not necessarily the right person to comment as I'm tainted by my frustration of an archaic and stupid system of taxation that ends up poisoning people.