Cleaning lead type

Alayne Alvis <alayne.alvis<-a t->sydney< . >edu< . >au> writes

>I have had an enquiry about cleaning lead type.  The person
>concerned is concerned about the toxicity inherent in any process
>that involves lead.  Would anyone with experience in this area be
>able to respond directly?
>...
>Do you think this set of actions will do the job and bearing in mind
>the toxicity issues is it safe for me and for the type?
>
>Should the solution in the ultrasonic bath consist of plain
>(distilled, perhaps?) water, or is there a better alternative?

I am an industrial hygienist and specialist in art and art
conservation issues.  My first question to this person is "why?"
Unless there is something extremely special about this particular
lead type, the stuff is a glut on the second hand art materials
market.  As type setting had been increasingly replaced by better
printing methods, and as lead environmental regulations have become
more and more restrictive, old type is being donated in bulk amounts
to art departments that just don't understand the hazards of using
and holding this stuff.  And in one school, they even have the old
molds so they can cast more lead type at will.  There really is no
way to tell the old from the new if the old molds are used and the
old type is melted down for casting.

I just inspected a school in Illinois just a few weeks ago that
probably has in total just short of a ton of this stuff.  Every year
I see schools with stock piles of the stuff since the donator then
doesn't have to pay to have it disposed of and can get a tax credit
that is worth more than selling it for scrap.  And my reports always
recommend the schools cease using it.  If they want to type set
using an historic method, fine.  Get a small computer driven wood
router (not very expensive now) and make wooden type.  And there is
still real old wood type available, too.  Why teach techniques from
the 1800s when they can go back to the Renaissance?

My reasons for recommending replacement are detailed in my report.
And if this person is interested, I will be happy to give her/him
the references for the studies showing that lead metal and lead
compounds skin-absorb significantly.  And the lead oxides and black
sulfur compounds that form on the surface of lead also shed as a
fine dust.  They shed enough to raise the lead content of dust in
the whole type setting area in schools where it is done above
current standards for safety.  The very idea of type setting lead in
a college or art school where women of child bearing age may attend
is just wrong.

But if there is a legitimate reason to clean the type, the
combination of dirt, oxides, and old ink should respond to a nice
long soaking in a commercial cleaner like Simple Green or any fast
household cleaner.  Be aware, however, that Simple Green and most
other fast cleaners are neither simple nor green.  They usually
function well by combining a powerful detergent and 2-butoxyethanol
in the range of 6%.  2-BTE is also completely water miscible.  But
it is skin-absorbing and very toxic with a very low air quality
standard here in the US and in the EU.  For this reason, I do not
recommend using these cleaners for household uses, but it would
certainly do a job on your type.  I would carry this out with medium
thickness nitrile gloves (since both lead and the 2-BTE skin absorb)
and under a hood to avoid inhalation of the solvent.  A very soft
brush should easily take any tough stuff off.

There is no purpose to using ultrasonic cleaning to get the type
pristine.  The type will redevelop a gray surface layer of oxides
and sulfur compounds no matter what you do.  And this it the natural
state of this type.

Good luck with the project, but be careful.

The American Conference of Governmental Industrial Hygienists
standards are the threshold limit values (TLVs).  I will use the 8
hour time weighted average standards for comparison with the German
Maximum Concentrations for the Workplace (MAKs).  I'll look at both
2-BTE and the other solvents you mentioned, citrus (d-limonene) and
n-methyl pyrrolidone, in comparison with safer solvents.  I leave it
to you to look up the Australian standards

    Chemical             TLV-TWA ppm       MAK-TWA ppm

    heptane                 400               500
    isopropanol             200               200
    2-BTE                   20                 10  skin absorber
    N-methyl pyrrolidone    not set            20  skin absorber
    d-limonene              not set             5  skin absorber

Monona Rossol, M.S., M.F.A., Industrial Hygienist
President:  Arts, Crafts and Theater Safety, Inc.
Safety Officer: Local USA829, IATSE
181 Thompson St. #23
New York, NY 10012
212-777-0062


                                  ***
                  Conservation DistList Instance 27:31
                Distributed: Thursday, February 6, 2014
                       Message Id: cdl-27-31-003
                                  ***