How to Read a Coating Technical Data Sheet
Every figure on a data sheet is true only under the condition printed beside it. Strip the condition off and the number becomes a guess. This is the field by field version, and the six ways a sheet gets misread.
A data sheet is not a list of numbers, it is a list of conditions. Every figure on it is true only under the condition printed beside it: a coverage rate at a film thickness, a pot life at a temperature, a recoat window at both ends. Read the condition first and the number second. The single most common misreading is taking a coverage figure without the thickness it belongs to, which is how one gallon of the same product can be quoted as covering 160.4 ft² or 53.5 ft² and both be correct. Put your own product into the film thickness calculator rather than reading a rate off a sheet and hoping it matches your build.
The one idea: every number carries a condition
Most of what goes wrong with data sheets is not that people cannot find the number. It is that the number gets copied out and the condition beside it gets left behind. A sheet says 30 minutes at 77°F and the note in the estimate says 30 minutes. A sheet says 160 ft²/gal at 10 wet mils and the order says 160 ft²/gal. In both cases the figure survived and the thing that made it true did not.
So the habit worth building is small and mechanical: whenever you write a figure from a sheet into a quote, a spec or an order, write the condition next to it. If the sheet does not state a condition for a figure that obviously depends on one, that absence is itself the finding, and the answer is to ask the manufacturer rather than to pick a plausible value.
Coverage is a curve, not a number
This is the field that costs money, so it goes first. Coverage is not a property of a product. It is a property of a product at a stated thickness, and the relationship is simple division: a gallon of 100% solids material spread one mil thick covers about 1,604 ft², so at 10 mil it covers a tenth of that and at 30 mil a thirtieth.
Run those two: 160.4 ft²/gal at 10 mil and 53.5 ft²/gal at 30 mil. Same product, same gallon, a factor of three between them. Neither figure is wrong and neither is the coverage of the product. They are two points on the line the hero above draws.
Simiron publishes exactly this pair for 1100SL: their sheet prints 160 ft²/gal at 10 wet mils and 53 at 30 wet mils. Note the word wet, because trap three below is exactly this confusion, and the only reason those figures can be set beside the dry film numbers above is that 1100SL is a 100% solids product, where wet and dry are the same measurement. On anything less than 100% solids the two columns are different numbers and cannot be compared this way.
With that established, the agreement is worth pausing on, because it is an independent check on the arithmetic this site uses. The constant came from first principles: a gallon is 231 cubic inches, so spread a thousandth of an inch thick it covers 231,000 square inches, and 231,000 divided by the 144 square inches in a square foot is 1,604. That derivation has never seen Simiron’s data sheet, and it lands on their printed figures. When a sheet and the arithmetic disagree, that is a signal worth chasing; when they agree, you can price with confidence.
Turn a sheet into a spread rate you can hold a crew to
Enter the solids figure off the sheet and the thickness your spec calls for. Returns theoretical coverage, coverage after losses, the wet film to set a gauge to, and a volume to order.
Returns 14.3 mil of wet film to apply, which is the number a wet film gauge can actually check
Open the live calculator →The fields that decide what you order
Three fields between them settle the material side of a quote, and they only work together.
Solids by volume
- The share of the tin that stays on the floor
- By volume, never by weight, for any thickness question
- An unlabelled single percentage is a question, not a number
- Worked through in full in the solids guide below
Coverage or spread rate
- Only meaningful with the film thickness attached
- Often quoted as a range because the build is a range
- Check whether the thickness quoted is wet or dry
- Theoretical, so losses come off it before you order
Kit size and mix ratio
- Kits rarely divide evenly into a floor, so round up
- A 2 gallon base plus a 1 gallon activator is a 3 gallon kit
- Ratio is by volume unless the sheet says by weight
- Both parts are sold together for a reason: no partial batches
The kit line catches people more often than it should. A sheet that quotes a mixed kit volume different from the pail you picture is not being unclear, it is telling you the parts combine to something other than the sum you assumed. Get that wrong on a floor priced to the gallon and you arrive a kit short. Once you have a volume, the epoxy coverage calculator does the round up to whole kits and splits Part A from Part B.
The fields that decide how the day runs
The second group does not change what you buy. It changes what is physically possible between the moment a pail is opened and the moment the floor is finished, and it is where a job goes wrong in real time.
Pot life and working time
- Quoted at a temperature, often at a mixed mass too
- Heat shortens it; a full bucket shortens it further
- Working time on the floor can differ from pot life in the pail
- Plan batches around the hottest part of the day, not the average
Recoat window
- Has a minimum and a maximum, and both matter
- Too early disturbs the coat underneath
- Too late means a mechanical bond instead of a chemical one
- Past the maximum the usual instruction is to abrade first
Cure stages
- Tack free, foot traffic and full cure are three different times
- Full chemical cure is what resists tires and chemicals
- Handing a floor back at foot traffic is how hot tire pickup starts
- All three are quoted at a temperature
The recoat maximum is the one that punishes you quietly. Miss the minimum and the floor tells you within the hour, because the coat underneath moves. Miss the maximum and everything looks perfect, right up until the coating starts letting go months later. On fast chemistries the window can close inside a single day, which is why the polyaspartic cure time calculator exists at all.
The fields that decide whether you should be coating today
The third group is the set of conditions the product needs from the room and the slab. These are limits rather than instructions, and a sheet that states one is telling you where its warranty stops.
Application temperature ranges are usually given for air and surface separately, and surface is the one that lags. Many sheets add a rule about the dew point, commonly that the slab must be several degrees above it, because coating a surface at or near the dew point traps moisture under the film. That check takes seconds in the dew point calculator and it is the difference between a clear coat and a milky one.
Moisture limits are the other common gate, stated as a relative humidity percentage inside the slab or as a vapor emission rate. If a sheet names a limit, that limit is a pass or fail test before the job starts, not a target to aim near. The concrete moisture calculator tells you which side of it you are on, and the moisture vapor barrier calculator sizes the fix when you are on the wrong one.
Six ways a sheet gets misread
Every one of these has a direction. They do not average out, and most of them fail towards ordering too little or coating too thin.
1. Weight solids used as volume solids
The weight figure is usually the higher one, so the product looks like it goes further than it does. You order short. Film thickness is a volume question; use the volume figure.
2. Coverage with no thickness attached
A sheet quoting roughly 100 to 300 ft²/gal with no film build named anywhere is not giving you a spread rate. A threefold spread anchored to nothing cannot be priced, and picking a point inside it is a guess wearing a citation.
3. Wet mils read as dry mils
They are the same number only at 100% solids. Below that the wet figure is always the larger one, and confusing them under specifies the floor. Set gauges to wet, write specs in dry.
4. Theoretical coverage used as an order quantity
The sheet figure assumes every drop lands at exactly the target thickness. Buckets, rollers, porous slabs and cut ins all take their share, so a loss allowance comes off before the order.
5. A reseller listing read as the data sheet
Reformulations change solids, coverage and cure times. A reseller page can carry a spec that was true two revisions ago. Go to the manufacturer, and note the revision date you priced from.
6. A range read as a point
When the sheet gives a range for both the rate and the thickness, the two ends often do not pair off in the way a quick read assumes. If the sheet will not give you a pair, the sheet is not the place to settle it.
Reading a sheet in order
A sheet is quicker to read in a fixed order than front to back, because the later answers depend on the earlier ones. This is the order that works.
Start with the revision date and confirm you have the manufacturer version. Read the chemistry and intended use, because a primer, a build coat and a topcoat answer to different rules and a sheet that covers several uses will quote several sets of figures. Take the solids by volume next, checking it says by volume. Then coverage, and specifically the thickness attached to it, noting whether it is wet or dry. Convert that to your own build in the film thickness calculator rather than accepting the sheet rate, because the sheet rate is for the sheet build.
Only then read the timing block: pot life with its temperature, recoat minimum and maximum, and the three cure stages. Finish with the limits, meaning application temperature, dew point rule and moisture tolerance, and the mix ratio and kit size. By that point every number you have written down has its condition beside it, which was the whole exercise.
What a sheet will not tell you
Worth being honest about the boundary. A data sheet describes a product under laboratory conditions on a substrate it assumes is sound. It does not know your slab, your crew, your building or the weather that week, and it will not tell you whether the floor needs grinding, whether the joints need filling, or whether the previous coating is still bonded.
It also cannot tell you what the job costs. A sheet gives coverage; a price comes from coverage plus losses plus labour plus everything else, which is what the cost per square foot guide works through end to end. Read the sheet for what it is authoritative about, which is the product, and take the rest from the floor in front of you.
Where to go next
The field that repays the most attention is solids by volume, because everything downstream of it is arithmetic: solids by volume and what a coating really covers takes it apart in full, and the coverage per mil chart is the whole curve as a lookup table so you can read any solids and thickness pair off one grid.
For the mix ratio, epoxy resin mixing ratios covers what an off ratio batch does and why the sheet means by volume unless it says otherwise. For the timing fields on the chemistry that moves fastest, polyaspartic cure time explained shows where a recoat window comes from and how much temperature moves it.
Frequently Asked Questions
What is the difference between a TDS and an SDS?
A technical data sheet tells you how to use the product: coverage, solids, mix ratio, pot life, recoat windows, cure times and the conditions each of those assumes. A safety data sheet tells you how the product can hurt you and what to do about it: hazards, personal protective equipment, first aid, storage and disposal.
You need both, and they answer different questions. Nothing on an SDS will tell you how far a gallon goes, and nothing on a TDS is a substitute for reading the hazard section before a crew opens a pail.
Why does the same product show two different coverage numbers?
Because coverage is not a property of the product. It is a property of the product at a stated film thickness, and a data sheet normally describes a range of builds.
Simiron 1100SL is the clean example: its sheet prints 160 ft²/gal at 10 wet mils and 53 ft²/gal at 30 wet mils. Both are correct, they are the two ends of the same line, and the difference between them is a factor of three. A coverage figure quoted without the thickness it belongs to is not a spec, it is one point picked off a curve.
The sheet gives one solids percentage with no label. Can I use it?
No. Treat that as a question for the manufacturer rather than a number to use.
Solids by volume and solids by weight are different figures, and the weight one is usually higher because the solid part of a coating is denser than the liquid part. Film thickness is a volume question, so volume solids is the answer. Using the weight figure in a coverage calculation makes the product look like it goes further than it does, which means you order short and the job stops.
What does the temperature next to pot life actually change?
Nearly everything about how the day runs. Pot life is quoted at a stated temperature and often at a stated mixed mass, because both drive the reaction. A sheet saying 30 minutes at 77°F is not promising 30 minutes at 90°F, and it is not promising 30 minutes for a full kit sitting in a bucket rather than spread out.
The practical version: heat and volume both shorten it. Mix smaller batches when it is hot, get the material out of the bucket and onto the floor, and treat the printed figure as the best case rather than the number you plan the bay around.
What happens if I miss the recoat window?
It depends which end you missed, and the two failures look nothing alike.
Too early and the coat underneath has not developed enough strength, so solvent or heat from the new coat can disturb it and you get wrinkling or a soft film. Too late is the more common and more expensive one: the previous coat has cured hard enough that the next one bonds to it mechanically rather than chemically, and the result is intercoat delamination that may not show up for months. That is why sheets print a maximum as well as a minimum, and why the usual instruction past the maximum is to abrade the surface before recoating.
How do I know the sheet I am reading is current?
Check the revision or issue date printed on it, and get the sheet from the manufacturer rather than from a reseller listing or a search result snippet.
This matters more than it sounds. Reformulations change solids, coverage and cure times, and a reseller page can carry a specification that was accurate two revisions ago. If you are pricing off a sheet, record which revision you priced off, so that when a floor behaves unexpectedly you can tell the difference between a product that changed and a job that went wrong.