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BOOK_ARTS-L  August 2012

BOOK_ARTS-L August 2012

Subject:

Re: Question about adhesives

From:

David Amstell <[log in to unmask]>

Reply-To:

Book_Arts-L <[log in to unmask]>

Date:

Tue, 21 Aug 2012 10:12:30 +1000

Content-Type:

text/plain

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Parts/Attachments

text/plain (65 lines)

Several people have asked further about EVA.

EVA is water-based, non-toxic, and easy to use.  It provides a considerably stronger bond than PVA.  We rarely use EVA at full strength, but mix it either with smooth paste or methyl cellulose to give extra working time.  It brushes and rolls out well.  Some of our colleagues use it in their case-making machines, and have found it very workable.  

It is useful to appreciate some of the factors associated with this class of complicated polymer.  All of the synthetic polymer systems have organic ingredients in them, whether they be EVA or PVA.  As such, there is a tendency for growths to develop.  Therefore, fungicides (or preservatives), are required in order to keep the formulas stable.  We have found that 2 - 3 years is a good shelf life for EVA, before it needs replacing.  It is after this time that the emulsion may turn very slightly yellow, or possibly develop smells.  But it also depends upon the fungicide used.  In this day and age, biocides and fungicides don't have a particularly good name because of their relative toxicity.  Therefore, an honest adhesive-maker will say that they are inclined to use low-level or relatively weak fungicides in their formulas.  This is an advantage from a health perspective, but the downside is that the adhesive systems don't have the strength over time to bear against the bacteria which like to grow in these emulsion systems.  It is for this reason, that, as bookbinders, we are told to keep our emulsions pure, and to always decant our adhesive from the main batch, and never pour it back in, and to keep all the lids on tightly when not in use.   This is true of EVA as well as of PVA.  If you treat your working container of EVA (or other synthetic adhesive) with care, it will last the distance, and will not grow any bugs, which is the cause of smells developing.  Our EVA, when mixed with paste or methyl cellulose, has never gone off in the 20 years we have been using it, as a result of these precautions in place.  We have had colleagues whose mix has gone off, but upon speaking with them, it was clear that they had not appreciated the value of keeping their containers clean, or of using pure or distilled water in their paste or Methyl Cellulose mixes.  PVA is not different, in terms of the care needed to be taken.  However, the PVA industry tends to use stronger fungicides, or at least fungicides in stronger concentrations, and this has likely given PVA a good name for stability.  We understand that formaldehyde is the main fungicide used by PVA factories around the world.  

EVA, from our understanding, is much more carefully formulated, particularly for conservation standards.  Excess or overly strong fungicides are avoided deliberately.  Nonetheless, fungicides are a fact of life and they are necessary where organic materials are used, and where water and air quality differs between regions.  Many EVA / paste / MC mixes in workshop environments can be easily tainted by dust and dirt particles, or even just tap water, and these alone can be the seed of a fungal infection.  Adhesive makers have an important job balancing all these factors when making the choice as to the correct fungicide and the strength to use when making up their emulsions.  What may have happened to a particular adhesive emulsion in one part of the world may simply not happen in another.  

Having said this, there is nothing to stop the wise practitioner adding a little of their own anti-fungal agent to their batches.  Many of you will want to use a natural remedy.  A few drops of tea tree oil mixed  in IPA has always been our mainstay solution when we want to enhance the health resistance of our EVA emulsions. 

We have found that EVA tends to be more costly than PVA, probably because there are not the economies of scale in its manufacture as there are with the supply of PVA around the world.  The Chinese are still sending out PVA by the multi-container load, to all corners of the world, but this doesn't give it any more  credibility:  PVA remains an inferior emulsion.  It requires unstable plasticisers to keep the film flexible, whereas the EVA molecule is innately flexible.  Be that as it may, PVA has its uses where conservation standards are less important.  In our opinion, in the bookbinding, conservation and related fields, EVA is the more suitable adhesive to use.

In the US, various companies sell EVA.  You yourself will have to approach some of the main suppliers and inquire which of their products is true, conservation-standard EVA - not just pH neutral, but an EVA which has been more attentively formulated.   In the UK, Evacon-R is an EVA formula, and it has undergone some tests by the British Library.  The Canadian Conservation Institute conducted a symposium on adhesives and consolidants in 2011, and this included discussions about EVA.  Their site has published the results.  The only EVA formula we are aware of which seems to be serious is one called Evasol, and it is made in Australia.  According to the product's specifications, it has passed the PAT (Photographic Activity Test), as well as having undergone extensive accelerated aging tests.

It is always useful to know something about the adhesives we all use daily, and especially the additives and the important part they play in the emulsion.

David Amstell

***************************************************************************


 -----Original Message-----
From: Book_Arts-L [mailto:[log in to unmask]] On Behalf Of shane and eleni
Sent: Sunday, 19 August 2012 7:51 AM
To: [log in to unmask]
Subject: Re: [BKARTS] Question about adhesives

Dear David,

 Thanks for that! Very informative.

 But, what is it like to work with?
 I have been told that it can be very smelly.

 What do you use?

 With thanks,
 Eleni Waugh.

 Austinmer, NSW, Australia.

----- Original Message -----
From: David Amstell
Sent: 08/18/12 01:43 PM
To: [log in to unmask]
Subject: Re: [BKARTS] Question about adhesives

 Bob, PVA is an old technology glue. It went out when people stopped believing in the existence of fairies (that's a long time ago!). EVA (Ethylene vinyl acetate) is the next generation adhesive. It is stronger and more stable in every way. But there is a lot of expensive infrastructure technology keeping PVA out there. Financial interests are very high in the PVA industry. In their hearts, though, the PVA companies know they are dealing with an old technology. For instance EVA is a naturally flexible molecule, and doesn't need added plasticisers. Whereas, in order for PVA to work, it has plasticisers added to the formula to give it flexibility. Plasticisers migrate to the surface long after the glue has "dried", and, according to our adhesive chemist, slowly break down with acidic residues. We gave up using PVA about 20 years ago in our bindery, and only use EVA. Our adhesive manufacturer realised the superior stability of the EVA molecule decades ago and gave up entirely making PVA at his industrial plant, and now only works with EVA. This is just our 2c worth. David


******** -----Original Message----- From: Book_Arts-L [mailto:[log in to unmask]] On Behalf Of [log in to unmask] Sent: Thursday, 16 August 2012 11:14 PM To: [log in to unmask] Subject: [BKARTS] 

Question about adhesives Hi, All. I'm working on some books that will involve adhering small wood panels to leather. Any recommendations for a better adhesive than PVA? For the curious, here's a link to one of our projects involving painted wood panels, lots of leather onlays and gold tooling. www.gildedleafbindery.blogspot.com Bob Roberts 

                                    
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