ALTANA Hoffman Scratch Hardness Operating Instructions

Measure what you see.

Hoffman Scratch Hardness Tester

A member of

Operating Instructions

Additives & Instruments

Hoffman Scratch
Hardness Tester

Operating Instructions

English

PE-1610

BYK - Gardner USA

9104 Guilford Road
Columbia, MD 21046
USA
Phone [phone]
301-483-6500
Fax [phone]
301-483-6555

www.byk.com/instruments

BYK-Gardner GmbH

Lausitzer Str. 8
D-82538 Geretsried
Germany
Tel. 0-800-gardner
(0-800-4273637)
[phone]
Fax [phone]

Description

Description

This instrument consists of an applicator blade
The Hoffman Scratch Hardness Tester was
developed by the National Paint, Varnish and
Lacquer Association and has been produced by
BYK-Gardner for many years. This instrument
was designed to fi ll the need for a simple portable
device to rate scratch resistance and adhesion of
industrial product fi nishes on a comparative basis.
It is an ideal tool for laboratory or fi eld use.

2

General Information

General Information

The Hoffman Scratch Tester consists of a four­wheeled carriage, a balanced beam with a
scale of 0-20 arbitrary units and a scratching
tool with a sharp circular rim mounted at 450 to
the test surface. a counterweight, allen wrench
and movable weights (riders) both large (100 g)
and small (25 g) are also included. The overall
dimensions of this instrument are 11“ x 11h“ x l „.

3

Operation

Operation

Before initial setup, please remove protective fi lm
from the scale arm (balanced beam). In operation,
small and/or large riders are attached to this arm
at the numbered positions. These must be placed
on the scale very carefully so that the test surface
is not marred before actual testing is begun. The
large rider generates a load of 100 grams per
division, while the small rider generates a load of
25 grams per division. The small quarter rider may
be used for marking low range measurements
involving small increments of pressure, or it may
serve as a vernier in conjunction with the large
rider in making more precise medium range
measurements. Two large riders may be used
for making high range measurements. The sum
of all the rider settings represents the total load
in grams applied by the lever system to the
scratching tool. The scale arm is counterpoised
and its graduation marks can be used with any
combination of riders to create a reproducible load
on the pivoted lever system. In order to assist you
in selecting the correct rider for your application,
listed below are several examples:

• Small quarter rider at position
4: 4 x 25 = 100 grams

• Large standard rider at position
20: 20 x 100 = 2000 grams

• Large standard rider at position 6, plus small
quarter rider at 2: (6 x 100) + (2 x 25) =
600 + 50 = 650 grams

• Large standard rider at position 20, plus
another large standard rider at position
10: (20 x 100) + (10 x 100) =
2000 + 1000 = 3000 grams

After attaching the rider(s), place the Hoffman
Scratch Tester on a fl at test surface that measures
at least 2“ x 4“. Place your hand on the carriage

4

Operation

platform directly over the pair of wheels nearest
to the scratching tool, using suffi cient downward
pressure to lift the counterpoised beam with the
selected rider at the 0 position. Pull the carriage in
the opposite direction from the scratching tool in
order to cause a trailing scratch. Move the tester
in a straight line making sure that the scratching
tool follows the rolling carriage in making both of
the following types of tests:

Cohesion: Start making tests for cohesion or
scratch resistance by moving the rider to
increase the load on the scratching tool until a
barely perceptible mark is made. Move the tester
(scratching tool) slightly before each new trial to
avoid marring the same surface more than once.

As an alternate procedure, compare the width
and character of the scratch made on a series
of test surfaces with the same load on the same
scratching tool. The scratch may be viewed either
with the unaided eye or measured under low
power magnifi cation.

Adhesion: First, mark off a panel to form a painted
edge, or cut a line all the way through the paint
fi lm to the substrate. Next, place the scratching
tool on the bare substrate at right angles to
the painted edge or cut. Start making tests for
adhesion or scrape resistance by moving the
selected rider to the left. Increase the load on the
scraping tool resting on the bare substrate until it
fails to ride up onto the test fi lm, but scrapes or
peels it away completely. Move the scraping tool
slightly before each new trial.

Another method is to compare the degree of fi lm
removal made by the same load and scraping tool
from a series of test surfaces.

5

Maintenance and Care

Maintenance and Care

The scratching tool should be rotated between
series of tests to equalize wear; and replaced
when the edge becomes dulled. It is made of
special tool steel and should give long service
on conventional fi nishes if used properly. Always
approach the fi nal reading from the lower end
of the scale to prevent overloading and dulling
the cutting edge against very hard substrates.
Do not lubricate the Hoffman Scratch Tester. To
maintain the tester in the best condition, keep it
free from dust and other foreign material. Handle
with reasonable care to prevent damage to the
pivotable beam and store the instrument in its
case when not in actual use.

6

253 017 659 EDFIS 0408 Europe