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  1. #1
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    Default PVA Glue off-gassing causing corrosion?

    SWMBO recently found three 9ct gold rings that were stored in a jewellery box I made for her a year ago had corroded to the point, in one case, of disintegration. The rings were held between cylindrical holders made by covering styrofoam with synthetic velvet. The fabric was stuck to the styrofoam using Titebond II, a cross-linked PVA glue. I've used this glue for the same application many times previously and never had any problem reported. A previous thread in this forum discussed corrosion caused by liquid drops of PVA glue, but a comprehensive google search has found no reference to off-gassing causing corrosion of jewellery.

    However, a paper looking at off-gassing of PVA glues used for making and lining clam-shell boxes for document preservation used a test which included exposure of lead and copper coupons to heated PVA. The lead exhibited corrosion products while the copper showed blackening, indicating the presence of acetic acid.

    In the bookbinding industry, a period of 30 days is recommended to allow for off-gassing, before use of the boxes. My recollection is that I completed my wife's jewellery box immediately before giving it to her, and making the ring holders would have been one of the last processes.

    I'll continue to research this, but in the meantime, I suggest that if you're making and lining jewellery or stationery boxes with PVA glue, you allow a month or so before selling them or giving them away.
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  3. #2
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    Thanks for that, Alex. Very interesting and helpful.

    I didn't know about the possible PVA issue, but I did become more cautious about using tanned suede when I read that some chemicals in the tanning process can cause discolouration of silver. I now use mostly Ultra-suede for linings. More expensive than pigskin suede but doesn't smell and is made from 80%+ recycled material.

    For attaching linings I now use DS tape wherever possible.

    Thanks again,

    Brian

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  5. #4
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    So THAT explains it! Some years ago I glued down some non-slip mat in a few tool drawers and bugger me if there wasn't a chronic rust problem soon after. I had thought that it was because it was a water based glue...or something, but is was set when I put the tools in. As it turns out, I was right it was "or something"

    It also explains why PVA starts to smell like vinegar when it gets old.
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  6. #5
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    I wonder if that is why I have constant corrosion problems with the chisels in drawers that have a lot of PVA in them to locate the individual holders.
    CHRIS

  7. #6
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    Quote Originally Posted by FenceFurniture View Post
    So THAT explains it! Some years ago I glued down some non-slip mat in a few tool drawers and bugger me if there wasn't a chronic rust problem soon after. I had thought that it was because it was a water based glue...or something, but is was set when I put the tools in. As it turns out, I was right it was "or something"

    It also explains why PVA starts to smell like vinegar when it gets old.
    I had the same issue. However I used double sided tape, not PVA.

    I wonder if the non slip mat (this was the perforated / mesh stuff) is hydroscopic

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    Quote Originally Posted by pippin88 View Post
    I had the same issue. However I used double sided tape, not PVA.

    I wonder if the non slip mat (this was the perforated / mesh stuff) is hydroscopic
    I changed to DS tape and it more or less fixed the problem. However, I suspect that there is a slight steel unfriendly ingredient in the non-slip mat because sometimes if a tool sits in the same spot for a while there is an "imprint" of the mat on it. Not rust as such, but very noticeable.
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    Most interesting Alex.

    I bought another conatiner of Titebond III just a couple of days ago. Apart from small amounts of epoxy glue I use it exclusively. I will be mindful where I stick it.

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    If you read the MSDS sheets for the various PVA glues you will note that they vary in pH values, but all are in the acidic range. Some will pose less of a potential hazard for rust corrosion on steel. No idea about the effect upon semi precious / precious metals nor the silver solders used to braze jewellery etc.

    Note a pH of 7 is neutral, less than 7 acidic, greater than 7 basic.

    AVXL Plus pH 4.0 - 5.0
    Selley's Aquadhere Interior pH 3.0 - 5.0
    Selley's Aquadhere Exterior pH 3.5 - 4.5
    Titebond I Original pH 3.8 - 4.7
    Titebond II Premium pH 3.0
    Sika pH 3.5
    Parfix PVA (Selleys) pH 4.0 - 6.0
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  11. #10
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    This seems to be a major issue.

    Why is it not advised on the bottle?

  12. #11
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    "Originally Posted by woodPixel"
    This seems to be a major issue.


    Why is it not advised on the bottle?
    Possibly because people would stop using it. This thread has started making me think of using hide glue instead of PVA. Does this means I can't even leave metal tools on my laminated work bench for fear of rust or it it only applicable in enclosed spaces?

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    Quote Originally Posted by BEM View Post
    Possibly because people would stop using it. This thread has started making me think of using hide glue instead of PVA. Does this means I can't even leave metal tools on my laminated work bench for fear of rust or it it only applicable in enclosed spaces?
    All products have benefits and less desirable traits. We simply have to learn to minimize the potential for the less desirable traits to cause harm / damage.

    The off gassing only occurs whilst the glue reaches "full cure" which may be days, months or years and then there is the potential for off gassing as the products age / deteriorate. Note the vinegar (acetic acid) smell of PVA glue.

    The acetic acid off gassing from mostly PVA glues is well known and poses significant risk for librarians and archivists with considerable technical research having been completed to minimize the risks of damage to documents, paper, and other significant artifacts. The "chemical stability" of enclosures (PVA), storage boxes and the furniture these containers etc are stored in is of concern. The long term stability sought by archivists includes any part of the storage system not degrading or producing harmful off gassing.

    For some glues particularly phenol / urea formaldehyde based glues used in particle boards and plywoods etc the gasses can pose health problems for humans and indeed animals, insects etc, hence the safe work procedures, standards and legislation to control the use of the products and to minimize exposure/s to potentially harmful VOC's (formalin / formaldehyde) etc.

    Perhaps a good reason to have product liability insurance if you are selling significant numbers of jewellery boxes.

    ps - look up "film preservation" - there is a major issue with "vinegar syndrome" causing irrecoverable damage to the old cellulose acetate film stock. Another illustration of the degradation of acetate based materials.
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  14. #13
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    Unless referring to a small enclosed container I think we are over blowing this folks.

    Rainwater has a pH of between 5 and 7
    Human sweat is between 4 and 5
    Beer is around 4
    Soda water is between 3 and 4
    Wine is 3.2 to 3.5
    and
    some soft drinks are as low as 2.5.

    If we're going to get knickers twisted over the pH levels in glue then maybe we'll have to wear gloves when handling tools and stop drinking in the shed?

    And of course there will be no farting because some farts contain H2S which dissolves in water to become sulphuric acid?

    I just looked up the pH wood and see its mostly between 4 and 5.5 although a few outliers are as low as 3.5 (Douglas Fir) and some are >7.
    pH varies within the same tree with sapwood usually around 5 and heartwood around 4.

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    Quote Originally Posted by BobL View Post
    Unless referring to a small enclosed container I think we are over blowing this folks.

    Rainwater has a pH of between 5 and 7
    Human sweat is between 4 and 5
    Beer is around 4
    Soda water is between 3 and 4
    Wine is 3.2 to 3.5
    and
    some soft drinks are as low as 2.5.

    If we're going to get knickers twisted over the pH levels in glue then maybe we'll have to wear gloves when handling tools and stop drinking in the shed?
    I agree to a point - how many wood workers have been dismayed to find rust on a tool, or a tool imprint on Jarrah, Tas Oak etc or discolouration from sweat drops on a piece, or some spilled Coke.

    It is an issue for document / jewellery boxes IF preservation is important, however the major risk of "vinegar syndrome" can be mitigated by simply letting the document / jewellery box "air" so that the PVA glue reaches "full cure" before being transferred to the new owner.

    ps wrt to "hide glues" there has been some research on the stability of liquid vs traditional hot hide glues and strength of wood bonds at varying relative humidity (RH) and also at elevated temperatures (150F) akin to leaving an item in a vehicle on a hot day. Hide glues lose significant strength above 50% RH. So storage environments also play a significant part in the long term stability and or degradation of items constructed with hide glues and indeed PVA glues.
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  16. #15
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    Quote Originally Posted by BobL View Post
    Unless referring to a small enclosed container I think we are over blowing this folks.

    Rainwater has a pH of between 5 and 7
    Human sweat is between 4 and 5
    Beer is around 4
    Soda water is between 3 and 4
    Wine is 3.2 to 3.5
    and
    some soft drinks are as low as 2.5.

    If we're going to get knickers twisted over the pH levels in glue then maybe we'll have to wear gloves when handling tools and stop drinking in the shed?

    And of course there will be no farting because some farts contain H2S which dissolves in water to become sulphuric acid?

    I just looked up the pH wood and see its mostly between 4 and 5.5 although a few outliers are as low as 3.5 (Douglas Fir) and some are >7.
    pH varies within the same tree with sapwood usually around 5 and heartwood around 4.
    My chisels suffer from corrosion and they are in shallow drawers with all the internals glued together. They are the only tools in my workshop to suffer the problem so it seems a reasonable conclusion to assume that the glue is a likely culprit but only a test against new drawers with no glue will tell the whole story.
    CHRIS

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