Quality testing of coatings, inks and raw materials is
required to ensure consistent production. Drawdown
charts have been used for many years for checking
color, gloss, opacity, hiding power, adhesion and many
other physical properties that are important to the
manufacturer of coatings as well as the end-user.

What happens when you discover that the new shipment
of drawdown charts that you are using is different from the
previous supply that you had been using? Can changes in
the color of the paper stock that was used to produce the
drawdown chart affect your results? What about changes in
the color of the coated white or black sections of the
chart? How can changes in the gloss properties affect your
testing? Any of these physical changes in the drawdown
chart can negatively influence your testing results and the
reliability of your standards. For example, hiding power or
coating opacity is measured by the lightness (L*) differences
of the coating on the white and black areas of a drawdown
chart. With a new batch of charts two possi b il ities can
happen if the L* of the white and black areas are not kept
consistent.

Case 1: If the black has a higher L* value than usual, the
difference between black and white is smaller. Less hiding
pigments are needed in the paint to make this difference
disappear; however when this paint is used on the wall to
hide stains, the stains show through. The contractor has to
apply a second paint layer, leading to increased material
and labor cost.

Comp White L

Comp White a

Comp White b

Comp Black L

Comp Black a

Comp Black b

Case 2: If the black has a lower L* value, the difference
between black and white is larger. The QC lab then orders
production to add more pigment to make the difference
disappear. Pigment is wasted, and the hiding power of the
paint does not improve when the paint is applied on the
wall. Inconsistent charts can lead to unnecessary costs,
produc tion adjustments and re-testing, only to discover that
the problems detected were due to variances in the chart
itself and NOT in the product being tested. To illustrate the
magnitude of the problem, consistency tests were con -
ducted on different production lots of a leading brand of
drawdown charts as well as our own byko-chartsŪ over a
period of 54 months.