CALCULATIONS ON PAINT FORMULAS
1. Density
Density of paint is:
Total sum by weight of each ingredient in paint
Total sum by volume of each ingredient in paint
2. Solid content
Solid content by weight of paint is:
Total sum by weight of each solid ingredient in paint x 100%
Total sum by weight of each ingredient in paint
Solid content by volume of paint is:
Total sum by volume of each solid ingredient in paint x 100%
Total sum by volume of each ingredient in paint
3. Pigment Volume Concentration
PVC paint is:
Total sum by volume of all pigments + extenders in paint x 100%
Total sum by volume of each solid ingredient in paint
4. Critical Pigment Volume Concentration
The best way to determine the critical PVC of a paint is to measure the volume of the dry pigment/extender mix of a paint in a centrifuge and to calculate the CPVC as follows:
CPVC = (calculated volume pigment/extender mix / volume after centrifuge) x 100
or
CPVC = ( f x G x 100) / (dPi x Va)
f = ratio weight pigments and total weight solid content paint
G = weight of dry film
dPi = density of pigment/extender mix
Va = geometric volume of paintfilm (e.g. 250 micron wet filmthicknes x length x width)
A theoretical calculation which estimates the approximate CPVC is:
CPVC = (volume pigment+extender x 100) / (volume pigment+extender) + ((average o.a. pigment+extender) / 0,93)
5. Extender replacement
To calculate an extender replacement by weight by another extender and maintaining PVC:
E = A1 x D2
A2 x D1
E = factor to multiply with original extender weight to calculate weight substituting extender
A1 = OA of original extender
A2 = OA of substituting extender
D1 = density of original extender
D2 = density of substituting extender
6. Crosslinking percentage of two component products
· Epoxies
Equivalent weight epoxy component base paint is:
Weight base paint
Weight epoxy resin (1) + Weight epoxy resin (2) +
Eq.w.epoxy resin (1) Eq.w. epoxy resin(2)
Equivalent weight amine component harder is:
Weight harder
Weight amine (1) + Weight amine (2) +
Eq.w. amine (1) Eq.w.amine (2)
Crosslinking percentage = Weight harder x Eq.w. base component x 100%
Weight base x Eq.w. harder component
Polyurethanes
Equivalent weight polyol component base paint is:
Weight base paint
Weight polyol resin (1) + Weight polyol resin (2) +
Eq.w.polyol resin (1) Eq.w. polyol resin(2)
Equivalent weight isocyanate component harder is:
Weight harder
Weight isocyanate (1) + Weight isocyanate (2) +
Eq.w. isocyanate (1) Eq.w.isocyanate (2)
Crosslinking percentage =
Weight harder x Eq.w. base component x 100%
Weight base x Eq.w. harder component
7. Calculation the amount of amine to neutralize waterreducible resins
Equation: A = R (AN) E
56.100
Where:
A = weight of amine
R = weight of resin, non volatile
AN = acid number resin, non volatile
E = equivalent weight of amine
8. Starting point amounts of hydroxy / carboxy / amide containing resins in melamine / urea resins combinations in oven cured systems
Let:
x = hydroxyl number (mg of KOH to neutralize the organic acid required to esterify the hydroxyl groups present)
y = acid number (mg of KOH required to neutralize one gram of resin)
z = amide number (mg of KOH equivalent to reactivity of the amide groups presentby calculation)
Then: 56 grams (mol.wt. KOH) = gram mol. of resin to be crosslinked
x + y + z (mg)
Example: the equivalent weight of a melamine resin is 130
If a polyester resin has a hydroxy number of 60, an acid number of 5 and an amide number of 0, the grammol weight of the polyester is:
56 grams = 861,5 grams
60+5+0 mg
Or the starting levels for the binder may be polyester / melamine resin = 861,5 / 130
Or polyester / amino = 87 /13 by weight on solids
9.Volatile Organic Compounds (VOC’s with vapour pressure > 0,01 kPa at 20 C)
VOC = weight volatile organic material (g/l)
Volume paint (without water
VOC = 100 – NV% – water% x 1000 (g/l)
(100/density) – water%
For solvent based coatings the formula simplifies to:
VOC = (100 – NV%) x 10 x density (g/l)
10.Theoretical spreading rate paint at given filmthickness:
Volume solids = liters/m2
Film thickness in microns : 10
Volume solids = kg/m2
(Film thickness : 10) x density solids paint
Price per m2 at given film thickness:
Price per liter
Theoretical spreading rate in liters
Relation thickness steel construction and surface:

11. Required air quantities to stay below MAC levels:
∑ ( TLV per ingredient x weight %)
12.Required air quantities to stay below lowest explosion limits:
∑ ( LEL per ingredient x weight %)
13.General formulae for mixing liquids
A = C – B
B = C (a – c)
a – b
C = B (a – b)
a – c
Where:
A = weight of original liquid a = its content in % by weight
B – weight of diluent b = its content in % by weight
C = weight of prepared mixture c = its content in % by weight
For water as diluent, b = 0
14. HLB (hydrophylic – lipophylic – balance) of surfactants and their activity features
0 – 4 = defoaming
3 – 7 = emulsifying
7 – 15 = penetrating
7 – 20 = emulsifying
12 – 20 = detergency
15 – 20 = solubilising
15.Mixing rules by using mixturecross
How much of each solution has to be mixed to get a 62% solid solution of a 54% solids solution with a 92% solids solution?
30 parts by weight of 54% solid solution must be mixed with 8 parts by weight of 92% solid solution to yield a 62% solid solution.
92 – 62 = 30 pbw 54% solution
62 – 54 = 8 pbw 92% solution
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Great post, very helpful.
Require calculations of epoxy hardner vs epoxy resin and also calculation of PU hardner vs PU resin
superb!!!! post