Glass beads/acid-washed

Matthew Sachs msachs at
Tue Sep 12 16:14:09 EST 1995

vldnaseq at wrote:
>I've purchased some glass beads for bacterial lysis with a bead beater. But I
>do not know the pre-preparation of the glass beads (Acid-washed?) and the follow
>-ing maintainence of these after use.  Would anyone share the experience?  Thank

This is a procedure we use for preparing glass beads (or sand) for fungal studies.

Use a fume hood and wear heavy rubber gloves, protective clothing and face/eye shields when working with acid like this.  Be sure all containers are resistant to acid.  It is a good idea to have a polypropylene tub under the beakers/trays used for soaking and washing beads so that acid dribbles and spills do not end up all over the working surface of the hood.

1) Put the beads in large glass baking dish or beaker.  Cover beads with 12N HCl.  Completely cover dish/beaker with glass plate (NOT ALUMINUM FOIL) and let sit overnight [other acid-proof vessels may work for this step].

2)  The next day, pour off acid into a tall receiving vessel.  The acid is likely to be yellow.  Use plenty of inexpensive baking soda to neutralize acid; add it very slowly to prevent acid from fizzing out of the vessel.

3)  Wash the beads with many rinses of deionized/distilled water.  Add water slowly to the beads that are in concentrated acid  (remember that routinely one should dilute acid by adding acid to water).  My impression is that after the first 10 or so rinses, it is better to let the beads sit in rinses for >5 minutes to allow acid to leach out, but this may be mistaken.  In any event, stir beads with a heavy glass rod to mix them.  The rinses need to be collected and neutralized as well.

4)  To determine when the beads have been rinsed enough:  stick pH indicator strips (nonbleeding) into the bed of beads.  Try different places.  When the paper always registers in the 5 range (pH of distilled water) you are through.

5)  Bake beads at 180 degrees centigrade in an oven with good airflow to dry them.

6)  This is a relative pain to do because acid is dangerous stuff.  Make a goodly amount so you don't have to do it often.

Matthew Sachs
Department of Chemistry, Biochemistry & Molecular Biology
Oregon Graduate Institute of Science and Technology
20000 NW Walker Road
P.O. Box 91000
Portland, OR  97291-1000
503 690-1487 Phone
503 690-1464 Fax
msachs at

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