Ralph

It strikes me that "safe" is not the endpoint; rather the endpoint is when
does the object cease modifying the pH of the extractant water. For
operational purposes, I would wear gloves until the pH of at least 2
consecutive extractions is <= 9.

The "what is safe" is a separate discussion that needs to address extent of
anticipated exposure. I agree with Kay that wearing gloves 100% of the time
leads to sloppy practices.

Hope this helps

nl

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-----Original Message-----
From: ACS Division of Chemical Health and Safety
[mailto:DCHAS-L**At_Symbol_Here**PRINCETON.EDU] On Behalf Of Stuart, Ralph
Sent: Monday, October 31, 2016 10:15 AM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: Re: [DCHAS-L] Upper limit of pH hazards

>why would one work actively in a chemistry lab without gloves?

The 3D printer pieces will not be used in the lab setting; there is concern
that the printed pieces could have micropores that retain corrosive liquids
longer than other types of materials. The student project will be to
determine the pH of the rinse water after each rinse to see how long it
takes to reach a "safe" level for the piece to leave the lab and enter the
world of things. Hence the question of what "safe" means.

Thanks to everyone for helping me to refine the question.

- Ralph

Ralph Stuart, CIH, CCHO
Chemical Hygiene Officer
Keene State College

ralph.stuart**At_Symbol_Here**keene.edu

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