Paint serves many purposes — it inspires, protects, disguises, depicts, decorates and identifies, yet many people give it no more than a passing thought. Making paint that is perfect for a demanding application is painstaking, but manufacturers go to great lengths to get it right. Viscosity testing is an important part of development, and the Stormer-type viscometer is the definitive instrument for the industry. Traditional viscometers measure viscosity in millipascal seconds, or mPas, while Stormer machines use Krebs units. Comparing results requires the conversion of mPas to Krebs.

## Intermediate Value

Note the viscosity in mPas that you wish to convert to Krebs. Write down the figure. If it is below 200 mPas or above 5,000 mPas, it lies outside the range for which conversion is possible.

Multiply the viscosity value by 0.1938 and add 36. Note the answer. For example, if the viscosity is 500 mPas, then the answer is 132.9.

Calculate the natural logarithm of your answer. Make a note of this intermediate value. For example, if your answer is 132.9, the intermediate value is 4.8896.

## Low Viscosity

Check if the viscosity is less than 2,100 mPas. If it is not, skip the remainder of this section.

Calculate the square of the intermediate value and multiply the answer by 0.0443. Record this second-power value. For example, if the intermediate value is 4.8896, then the second-power value is 1.0591.

Multiply the intermediate value by 0.8542 and record this first-power value. For example, if the intermediate value is 4.8896, the first-power value is 4.1767.

Add 1.1187 to the first-power value and subtract the second-power value. Record the answer. For example, if the first-power value is 4.1767 and the second-power value is 1.0591, the answer is 4.2363.

Calculate the inverse logarithm of your answer and note the result. For example, if the answer is 4.2363, the result is 69.1515.

Check each step of the calculation carefully. Record the result, which is the viscosity in mPas converted to Krebs units.

## High Viscosity

Check if the viscosity is at least 2,100 mPas. If it is not, skip the remainder of this section.

Calculate the square of the intermediate value and multiply the answer by 0.0206. Record this second-power value. For example, if the intermediate value is 6.2548, then the second-power value is 0.8059.

Multiply the intermediate value by 0.596 and record this first-power value. For example, if the intermediate value is 6.2548, then the first-power value is 3.7279.

Add 1.8118 to the first-power value and subtract the second-power value. Record the answer. For example, if the first-power value is 3.7279 and the second-power value is 0.8059, the answer is 4.7338.

Calculate the inverse logarithm of your answer and note the result. For example, if the answer is 4.7338, the result is 113.7269.

Check each step of the calculation carefully. Record the result, which is the viscosity in mPas converted to Krebs units.

#### Tips

If you do not have a scientific calculator, use online calculators to do the conversion (see Resources 2 and 3).

#### Warnings

Stormer-type viscometers are only suitable for measuring a limited range of viscosities. If you convert viscosity values that fall outside this range, the results will be meaningless.

#### References

#### Resources

#### Photo Credits

- Ableimages/Photodisc/Getty Images