Novolac
A phenolic epoxy resin carrying far more reactive sites than standard bisphenol A epoxy, which cures into a much denser network. That density is the whole product: it is what resists acids and solvents, and it is the reason novolac is the right call on a small number of floors and money thrown away on the rest.
What novolac actually is
Novolac is a resin, not a grade, a brand or a quality tier. Where a standard epoxy is built on bisphenol A, a novolac epoxy is built on a phenolic resin that carries considerably more reactive sites along each molecule. When it cures, those extra sites mean many more connections form, and the result is a much denser three dimensional network.
That density is the entire product. A chemical attacks a coating by getting in among the polymer chains and working on them, and a tighter network gives it less room to enter and fewer weak points to exploit once inside. Everything novolac is good at, and everything it is bad at, follows from the same fact.
What the density buys, and what it does not
It buys resistance to things that attack chemically: concentrated acids, aggressive solvents, and the sustained heat that would soften an ordinary epoxy film. That is a real and substantial gain, and on the floors that need it there is no cheaper way to get it.
It does not buy toughness. A stiffer, more highly crosslinked film has less give in it, so novolac is generally the more brittle of the two under impact at the same thickness. A dropped cylinder or a steel wheel with a flat spot is not a chemical problem, and the denser network is no help against it.
It also buys nothing at all against sunlight. Novolac is still an aromatic chemistry, and the reason standard epoxy ambers applies to it unchanged. Chemical resistance and light stability are separate properties of a coating, and it is easy to assume the more expensive resin must be better at both. It is not.
When it is right, and when it is money thrown away
The specification follows the exposure, and nothing else. A floor that sees concentrated acid, strong solvent or real heat has a case for novolac: chemical process areas, secondary containment, battery charging rooms, parts of food and pharmaceutical production. On those floors a standard epoxy is not a cheaper option, it is a floor that will fail.
Almost every other floor has no case at all. A garage, a warehouse aisle, a showroom, a gym: standard epoxy already handles what those buildings actually spill, and novolac adds cost to the quote and difficulty to the installation in exchange for resistance nothing there will ever test.
So the question to settle before choosing a resin is not which resin. It is what gets spilled, at what concentration, and how long it sits before anybody deals with it. A dilute cleaner wiped up in a minute and a concentrated acid left overnight are different floors, and only the second one is asking for this.
What it changes about the day
Treat a novolac product as one you have not used before, because in the ways that matter you have not. Viscosity, how long the mixed material stays workable, and what the primer underneath has to be all commonly differ from the standard epoxy in the same van. Carrying across the numbers you know is how a first novolac job goes wrong, and reading the sheet properly matters more here than on a product you have laid a hundred times.
The mix ratio deserves particular care. On any epoxy an off ratio gives you a weaker floor; on this one it undermines the specific thing being paid for, because the chemical resistance is the cured network and an incomplete reaction is an incomplete network. The resin mixing ratio calculator will give you exact volumes for whatever batch size you are working in.
One last point about how these floors are usually built. Novolac often appears as the topcoat over a standard epoxy body, which is sensible, since attack happens at the surface and thickness is cheaper to buy lower down. What that arrangement cannot tolerate is a route through it. A crack, a pinhole, a holiday or a spot worn back to the layer beneath gives the spill access to a resin nobody chose for it, so on a novolac floor a defect in the film is a more expensive thing to have than on an ordinary one.
This page prints no figures, deliberately. How much more resistant, how much dearer, and how much shorter the working window runs are all product specific, and a number invented here would read as a benchmark to hold your own product against. The sheet in front of you is the authority.
Frequently Asked Questions
Does my floor need novolac?
Almost certainly not, unless something specific gets spilled on it. Novolac earns its cost where a floor sees concentrated acids, aggressive solvents, or sustained heat: chemical process areas, secondary containment, battery charging rooms, some food and pharmaceutical production.
A garage, a warehouse aisle, a showroom or a gym is not that floor. Standard epoxy already resists the things those floors actually meet, and specifying novolac for them adds cost the job cannot justify and a product that is harder to install well.
The question to answer first is not which resin, it is what gets spilled, how concentrated it is, and how long it sits before anyone wipes it up.
Is novolac just a higher grade of epoxy?
No, and that framing is what leads to it being specified wrongly. It is a different resin backbone rather than a better version of the same one, so it is not uniformly stronger. It trades.
The dense network that resists chemical attack is also a stiffer, less forgiving one, so novolac tends to be more brittle under impact than a standard epoxy of the same thickness. Treating it as a straight upgrade means paying more for a floor that is better at something your building never does and worse at something it does daily.
Will novolac stop my floor turning yellow?
No. Novolac is still an aromatic chemistry, so it ambers under ultraviolet light exactly as standard epoxy does. Chemical resistance and light stability are unrelated properties, and buying more of one gets you none of the other.
If sunlight reaches the floor, the answer is the same whichever epoxy is underneath: an aliphatic topcoat, which means a polyaspartic or an aliphatic polyurethane. Our page on a yellowing epoxy floor covers why that is a chemistry problem rather than an installation one.
Does novolac install like the epoxy I am used to?
Assume not, and read the sheet rather than carrying your usual numbers across. Novolac products commonly differ from a standard epoxy in viscosity, in how long the mixed material stays workable, and in what they demand of the primer underneath.
The mix ratio matters more here than anywhere, because the chemical resistance you are paying for is a property of the cured network. An off ratio does not simply give you a slightly weaker floor, it gives you an incompletely built network, which is the exact property the specification was bought for.
Can novolac be used as a topcoat over standard epoxy?
That is a common way to build these floors, and it is often the sensible one. The build coat provides thickness and cost effective body, and a novolac layer at the surface does the chemical resisting, because attack happens at the surface.
What that arrangement cannot survive is anything reaching the layer underneath. A crack, a pinhole, a holiday or a coating that has been abraded through gives the spill a route to a resin that was never chosen to handle it. So a novolac topcoat raises the price of a defect in the film as well as the resistance of it.