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Subject: Re: [DCHAS-L] FW: Inquiry from an art conservator

Date: Mar 27, 2025 22:05 UTC

Author: James Saccardo <James.Saccardo**At_Symbol_Here**CSI.CUNY.EDU>

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Subject: Re: [DCHAS-L] EPA Methylene Chloride Monitoring

Date: Mar 28, 2025 15:22 UTC

Author: Ingrid Gm <ijgm147**At_Symbol_Here**GMAIL.COM>

From: Monona Rossol <0000030664c37427-dmarc-request**At_Symbol_Here**LISTS.PRINCETON.EDU>

Subject: Re: [DCHAS-L] FW: Inquiry from an art conservator

Date: Mar 27, 2025 22:15 UTC

Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>

Message-ID: <2069256209.1490985.1743113705318**At_Symbol_Here**mail.yahoo.com>

In-Reply-To: <d46bdb83-cba5-4cda-b0ab-bacd4296aa58**At_Symbol_Here**well.com>

Demystify: 
You can google the subject and find a lot of papers.  This is a well-known problem and this is a solution that has been used for 35 years. We can't argue with success.  The darkened pigment is treated and it turns bright white again.  However, our conservator is wrong about the chemistry as you correctly surmised.

From my understanding of the problem, lead white pigments are traditionally a mixture of cerussite (PbCO3) and hydrocerussite (2PbCO3·Pb(OH)2). The presence of hydrogen sulfide in polluted air leads to darkening of the pigment from formation of grey or black lead sulfide.  And this is the compound that is converted to lead sulfate.  
2PbCO3 · Pb(OH)2 + 3H2S 3PbS + 3H2O + 2CO2

But the issue of safety is the core of her question.  Clearly, conservators are going to do this and throw their chemicals away after using them.  Any wisdom on the hazards, precautions and disposal would be greatly appreciated.

Monona

On Thursday, March 27, 2025 at 04:16:49 PM EDT, davivid <davivid**At_Symbol_Here**well.com> wrote:


Do you have a reference for the procedure? I'd love to know how to
convert a carbonate into a sulfate using hydrogen peroxide.

As for the peroxide/ether solution I would kill the peroxide with
aqueous sodium bisulfite or thiosulfate. As an alternative to ethereal
hydrogen peroxide there are organic hydroperoxides such as t-butyl
hydroperoxide but I'm not sure that would be any safer.

Thank you
Dave Lane

CSO Zyviva Labs

On 3/27/25 10:34 AM, Membership Chair wrote:
> *From:*Monona Rossol <actsnyc**At_Symbol_Here**cs.com>
> *Sent:* Thursday, March 27, 2025 4:57 AM
> *To:* Ralph Stuart <membership**At_Symbol_Here**dchas.org>
> *Subject:* Inquiry from an art conservator
>
> All y’all on the DCHAS list
>
> An art conservator contacted us with a question that is beyond us.  And
> there are so many on this forum endowed with wisdom on peroxide
> formation and disposal rules that I thought this would be the best place
> to post.  You can answer this email for the edification of all
> (preferred method) or contact me personally at actsnyc**At_Symbol_Here**cs.com
> <mailto:actsnyc**At_Symbol_Here**cs.com> and I’ll put you in touch with the conservator.
>
> I look forward to your help.
>
> Monona Rossol, President
> Arts, Crafts & Theater Safety
> New York NY 10012
>
> THE INQUIRY:   Thank you both for getting back to me so quickly! If you
> wouldn't mind, posting on the forum would be much appreciated. Here is
> the goal and the protocol:
>
> We would like to convert discolored white lead carbonate pigment into
> white lead sulfate using an ethereal hydrogen peroxide. The procedure
> for this was established in the 1990s to create a non-aqueous delivery
> method for the peroxide.
> Equal parts 20 volume hydrogen peroxide and diethyl ether are shaken
> together and then left to settle to separate the aqueous component. The
> ethereal hydrogen peroxide is then brushed onto the discolored lead sample.
>
> Questions: What should be done with the used peroxide and ether
> solution? How should we store the diethyl ether? Is there a form of
> diethyl ether that is safer to use/store?
>
> Our lab has one cabinet for flammables, one for corrosives (with two
> sides, acids and bases), and one vent to the outside that is connected
> to the flammables cabinet. We have two fume hoods, one ducted and one
> standalone. We have the Novec Fire Suppression system in our collection
> storage, but the rest of the lab is fire-extinguishers only. Our
> chemical disposal company has agreed they can take the diethyl ether
> wastes but have not specified whether it should be a separate waste
> stream or a specific container. Guidance would be much appreciated.
>
> Many thanks!
> -Joanna
>
> --- For more information about the DCHAS-L e-mail list, contact the
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