pellets are easy to make if a few simple rules are
followed. First, heat the anvils and the body of
the die set before you make your pellet. This makes
them as dry as possible. Second, use dry KBr powder.
Third, make sure that the anvils, the die set and
the powder are all the same temperature. Hot powder
and cold anvils will produce a cloudy wet pellet.
Heating the KBr powder in a dry environment will
dry it out and storing it in a heated case or desiccator
will keep it dry. If you cannot keep the KBr powder
dry, try grinding your own powder from random cuttings
of KBr. This can be simplified by using a Wig-L-Bug
mill. Using too much KBr powder is one of the most
common mistakes. Use as little KBr powder as possible
- usually just barely enough to coat the
anvils of the die set so that the face of the anvil
is completely and evenly covered with a very
thin coat of powder. To compress an excessive amount
of powder requires considerably more force on the
press than is required if the proper amount of powder
is used; and if inordinate force is not applied
to the excessive powder charge, the pellet will
either wedge or contain white spots. Grind the sample,
not the KBr powder. Grinding the KBr powder opens
crystal facets which absorb moisture. Mix (do not
grind) the sample into the KBr powder. Last, if
you are pulling a vacuum on a die set, make sure
that it is properly assembled and that the seals
are in good condition and are positioned where they
belong. Detailed pellet making instructions applicable
to specific accessories are available with all ICL
presses and dies.
presses are used for a variety of tasks, but the
bulk of the applications involve pressing sample
pellets from a matrix of KBr and an organic sample
for infrared spectroscopy, briquetting inorganic
samples for x-ray fluorescence (XRF) spectroscopy,
and pressing thin polymer films using heated platens
for transmission sampling by IR spectroscopy. There
are, however, numerous other applications such as
pill making and laminating. There are also alternatives
to lab presses, such as ICLs new Roto-Film
and Tensioner accessories for producing thin
to Consider When Selecting A Lab Press
the right lab press for your application typically
involves an evaluation of the following issues:
much load or force will you have to put on the
much room do you need inside of the sample compartment
of the press?
is the daylight opening and the size of the platens?
much strength or energy (work) is required to
pump the press up to the required load?
the rate of ramp up to the desired clamp force
or ramp down from load be controlled?
much space do you have for the press in your lab?
you have to move the press?
much does it cost for the features you require
and how much will be added to that cost for optional
I Really Need A Hydraulic Press?
you are doing briquetting for XRF, the answer is
yesthere is no alternative. If you are doing
KBr pellets, you should first consider a hand press.
presses make excellent transparent KBr pellets with
minimal work. They require virtually no lab space
and they are portable. Furthermore, they are relatively
easy to operate. The major drawbacks of hand operated
presses are that they do not lend themselves well
to creating samples that can be stored for future
reference and they are either not evacuable or cannot
be evacuated with the efficiency of a die set designed
for a hydraulic press. If you keep your powder dry
and your anvils heated, water absorbances can be
minimized (see above Making KBr Pellets).
Extra collars for hand press die sets can solve
short term pellet storage needs. But, if you are
going to make a large number of KBr pellets that
must be very dry or that you intend to store in
large quantities, you will need a hydraulic press.