Flugger acrylic putty

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The widespread use of the commercial product Flugger Acrylic Putty
amongst the conservation community worldwide is becoming
increasingly apparent.  However, as far as I am aware, this use
appears to have crept in without any notable testing or peer review
publication as to its efficacy as a 'conservation grade' material.
In many leading institutional conservation departments and the
private sector, it is used as a filler and for fine surface
finishing of small losses and chips etc, as well as larger missing
areas on traditional and contemporary paintings, sculpture, ceramics
and other artifacts.  Its attraction is both its convenience and
that it shows less shrinkage than many commonly used commercial and
'in-house' made alternatives.

A fine acrylic paste stabilized in water and composed of butyl
methacrylate and calcium carbonate, 'Flugger' may be thinned or
cleaned up during application using water, it may be polished to a
very smooth finish, it takes a caste or moulded surface texture
well, it may be tinted using acrylic paints or dry pigments, and it
is quick drying.  Whilst it has been primarily marketed as an
artists' material by its Danish manufacturers, it is for example
excellent for matching glassy smooth finishes on thick household
paint surfaces in the restoration of many contemporary paint films.

In the UK, the suppliers Conservation Resources Ltd market it as
follows:

    ... An excellent bonding and filling acrylate filler which,
    after grinding and dusting, can be painted with aqueous or alkyd
    paint. It is suitable for spot filling and for finishing filling
    of primed woodwork, plaster, concrete, anti-corrosion iron and
    metal as well as previously painted surfaces. It can also be
    applied in a relatively thick layer without cracking. Wood
    conservators and framers use Flugger to fill missing areas, and
    it can be sanded when it is dry. Pigments can be added to colour
    Flugger, and it is also used to build up missing areas on
    acrylic and other media paintings.

        Solids weight 77%;
        volume 59%;
        density 1.8 kilo/litre;
        layer thickness maximum 2 mm;
        particle size max 0.01 mm;
        adhesion 12kp / cm2

        Thin or clean it using water.
        Drying time at 68 deg. F (20 deg. C) 60%RH is approximately
        1/2 hour (dry to the touch).

        Re-coating interval is approximately 1 hour; the finished
        product is fully cured in several days.

    Referenced by

        Koob, S.P.
        "Restoration skill or deceit: manufactured replacement
        fragments on a Seljuk lustre-glazed ewer",
        in The Conservation of Glass and Ceramics; Research,
        Practice and Training Norman H. Tennent (ed), James and
        James Ltd., London, 1999, p.157.

It has been recently reported to me that Flugger has the potential
to be affected by fungal activity.  Whilst I and my studio have been
using it successfully for a number of years without problem, I have
experienced mold growth in half used tubes in 2004, during my tenure
as Head of Conservation at the City and Guilds of London Art School.

This same problem appears to be found by some other conservators
whilst others have had no problem at all. So far as I know, no mold
growth has been found on finished surface fills to damages which
would normally be sealed between layers of methacrylate or
polycyclohexanone varnishes anyway (certainly in paintings).  Some
tests have been carried out by at least one conservation department
but this was on colour stability (which was ok) not fungal issues.

As we use such small amounts at any one time, these tubes can often
be stored in the studio for quite a while.  The tubes are quite
large and stiff so that when they are half full the rest of the tube
has trapped warm (room temperature) air when the lid is on and it
seems more likely that a trapped contaminant is going moldy rather
than the paste itself.  I therefore queried the manufacturers which
produced the following rather meagre response: "As this product does
not contain any fungicide we can not guarantee that no growth will
occur on surfaces filled with this Filler."  Consequently I sent the
following reply:

    Would you therefore:

        Advise we store the tubes in a fridge?

        Advise we add a fungicide to each tiny amount taken out of
        the tube to use?

        If so what fungicide would you advise we use?

        Consider manufacturing and supplying a modified version with
        you own fungicide added?

        Consider manufacturing and supplying a modified version in a
        smaller squeezable tube that you can roll up the end (like a
        toothpaste tube) ensuring that all air is expelled before
        replacing the cap? (This last option might be very popular)

I am still waiting to hear back from them.  Meanwhile, it has been
suggested that we might decant new tubes into smaller sterilised,
air tight containers and refrigerate, discarding any part used
container on the first sign of any problems?

Does anyone else have any direct experience of mold problems with
Flugger? Should we stop using it?  Whilst 'as is' it obviously has a
limited shelf life, but is it okay to use when new and no mold is
apparent?  Does anyone have any other thoughts on how this might be
caused and whether this might be an inherent problem with the
product itself?  Has anyone carried out tests relating to this issue
/its use in the conservation profession, and has anyone published
(or is intending to publish) any conservation data on the use of
Flugger as a conservation grade filler?  I would be grateful for any
comments, general or otherwise.

Kiffy Stainer-Hutchins
Kiffy Stainer Hutchins and Co
Conservation and Restoration of Fine Paintings and Associated Works
Houghton Conservation Studios
Houghton
Norfolk PE31 6TY
United Kingdom
+44 1485 528 667


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                  Conservation DistList Instance 23:5
                  Distributed: Thursday, June 11, 2009
                        Message Id: cdl-23-5-020
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