According to the MSDS for Novus 2, it is:
60-70% water by weight
7-13% mineral spirits by weight
Millwax - at least the closest MSDS I can find, says:
75-80% Isoparaffinic hydrocarbon solvent by weight
Here's a little explanation of the above:
Isoparaffinic Solvents
Isoparaffins are oil-like solvents and are derived from a petrochemical base using catalytic synthesis. This class of solvent contains pure hydrocarbons. The products most useful for industrial cleaning contain a mixture of fully saturated, linear and/or branched aliphatic hydrocarbons in the range of around C9 to C13. The flash point of these products is typically in the 57 to 65°C range which equals a boiling point of between 180°C and 220°C. Depending on the product, the boiling range may be as narrow as 10 to 15°C.
Isoparaffinic solvents are virtually free of aromatics compounds, are completely saturated and are practically odorless. They are good for the dissolution and removal of oil residues from metal surfaces. Additionally, they are excellent degreasing agents in numerous applications. However, as the solubility of polar substances in hydrocarbon solvents is extremely low, this may result in incomplete cleaning when the contamination contains polar components such as residues of aqueous emulsion and /or polar additives from high performance cutting fluids. Moreover, hydrocarbon solvents can not be stabilized against acidification. Acids brought in as part of contaminations or produced by decompositions may accumulate in the cleaning system and lead to acidification and corrosion.
Having said that (!).....I use Novus exclusively. It's not as if you are dumping a 6" puddle on your playfield and letting it sit there for an hour or anything. And frankly, to me, a little water and mineral spirits is more comforting than " Isoparaffinic solvents" which "cannot be stabilized against acidification". Whatever you decide, use it with common sense, clean it up and finish with a 100% carnuba wax and you will be fine.