Customers often ask, “How do we estimate the amount of water based coating that it will take to run a job?”
The answer is “make it easy on yourself”! Re-quest from Cork the now available coating usage calculator and skip the math below.
There are practical limits to the maximum amount of wet coating that a given coater design can apply. This is deter-mined by the general design of the coater and the limiting factors that are present. We suggest that you first make reference to the specifications and procedures offered by the manufacturer of the coater to determine what they recommend.
You will find that there are differences between coater designs and the capability that a given design has to carry and transfer aqueous coating to a substrate. However, generally speaking, the coating industry talks in terms of applying aqueous coating at the rate of 1 pound wet, per thousand square feet (MSF) of substrate surface to be coated, to achieve coating formula design properties. Some printers will choose to apply more or possibly less than 1 pound wet/MSF to achieve their specific goals for aqueous coating.
We can therefore say, one thousand square feet (MSF) is equal to 144,000 square inches or 12″ x 12″ x 1000, and this area requires 1 pound of aqueous coating. Aqueous coating can be said to average 8.65 pounds per gallon for a typical formulation. Naturally, there are coatings that will weigh slightly more and some slightly less depending on specific formulation, and of course, the percent of solids contained. These variations may be found on technical data sheets and MSDS. It follows that a 55 gallon drum will weigh about 470 pounds. Again check the drum label for the specific formula to determine the pounds of coating in a drum.
Formula for determining job coating usage illustrated with example IF:
Sheet size = 25″ x 38″
Coated area = 24.5″ x 37.5″
Job number of sheets = 20,000
Sides of sheets to be coated = 2
(Note: this example 2 side coated) THEN:
COATED LENGTH OF A SHEET X COATED WIDTH OF A SHEET X NUMBER OF SIDES OF SHEET TO BE COATED = TOTAL COATED SQUARE INCHES OF A SHEET.
24.5″ x 37.5″ x 2 = 1,837.5 SQ. IN.
TOTAL COATED SQUARE INCHES OF A SHEET X TOTAL NUMBER OF SHEETS IN JOB = TOTAL COATED SQUARE INCHES IN THE JOB.
1,837.5 x 20,000 = 36,750,000 SQ. IN.
TOTAL COATED SQUARE INCHES IN THE JOB – 144 = TOTAL SQUARE FEET TO BE COATED.
36,750,000 – 144 = 255,208 SQ. FT.
TOTAL SQUARE FEET TO BE COATED – 1000 = NUMBER OF POUNDS OF COATING NEEDED
255,208 – 1000 = 255.2 LBS. FOR 2 SIDES. (1 SIDE = 127.6 LBS.)
NUMBER OF POUNDS OF COATING NEEDED – COATING WT. POUNDS PER GALLON = GALLONS OF COATING NEEDED.
255.2 – 8.65 = 29.5 GAL. FOR 2 SIDES. (1 SIDE = 14.75 GAL.)
This formula may be extended as follows to allow the determination of applied dry coat weight.
TOTAL SQUARE FEET TO BE COATED – 1000 = TOTAL NUMBER OF MSF COATED AREAS.
255,208 – 1000 = 255.2 MSF COATED AREAS.
POUNDS OF COATING USED – TOTAL NUMBER OF MSF COATED AREAS = POUNDS OF COATING WET WT. USED PER MSF.
255.2 – 255.2 = 1.0 LB.
POUNDS OF COATING WET WT. PER MSF X % SOLIDS IN THE COATING = POUNDS OF COATING DRY WT. USED PER MSF.
1.0 x 40% = .4 LB.
If the pounds of coating used in the example above were known to be 310 lbs for example, THEN:
310 – 255.2 = 1.2147 LB COATING WET WT USED PER MSF.
1.2147 X 40% = .486 LB COATING DRY WT USED PER MSF.
To estimate the amount of coating required to spot coat 1 side, estimate the percent of coating coverage and multiply the number of pounds required for overall coverage by the percent of spot coating coverage. Divide by coating wt. per gallon to find gallons needed.
50% COVERAGE = 127.6 LBS. X 50% = 63.8 LBS. – 8.65 = 7.38 GAL.
LOOK TO CORK!……. for your coating and varnish needs, for both aqueous & UV/EB coatings/ and varnishes.