ALUPV 250 or PP250L as a protective backing for paintings

    **** Moderator's comments: Please respond directly to the
    author.

ALUPV 250, otherwise known as PP250L, and sold in the UK under the
latter by Protective Packaging Ltd in Sale, Cheshire, is
increasingly being used in paintings conservation, both
institutionally and privately, as a protective thermal insulation
backing for paintings hung in uncontrolled and potentially adverse
environments.  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.  I understand
it was developed in the packaging industry primarily for protection
of sensitive electronics and for food where temperature fluctuations
may be an issue.  Its advantages in preventive paintings
conservation are its notable insulation performance and ease to fix
and remove quickly with no invasive or permanent intervention.  It
can be stapled or taped to the reverse of a frame and can
accommodate uneven and difficult shapes and surfaces.

ALUPV 250 /PP250L is a flexible, fairly thick and robust triple
laminate of low density polythene (LDPE), aluminium foil and a white
Polyester flock lining for insulation on the inner face.
Communications with Protective Packaging state that "The LDPE, which
is used as a sealing layer when manufacturing bags from this
material, covers the outside of the aluminium. The aluminium is
sandwiched between Polyester and LDPE.  The adhesive used is a
solvent based adhesive which is specially formulated for the
lamination process.  We would expect the foil to be stable for up to
20 years providing it is kept between -40 and +80 deg. C and of
course it must be maintained in good condition."

The effect of sunlight/UV on the polythene would dramatically
decrease its longevity, but this should not be a problem when
face-in to a wall on the back of a painting.  Current thoughts are
that a 20 year life is conservative, but that when degradation does
occur it will be the polythene first and that at worst this might
produce harmless paraffin derivatives. The technical data states:

    Construction

    90 g/m2 Polyester Non Woven;
    45 g/m2 LDPE Coating;
    12 micron Aluminium Foil (32 g/m2);
    3 g/m2 Adhesive;
    73 g/m2 LDPE Film

    Technical Values / Performance

    Total Weight (g/m2) approximately 243 gsm EN 22 286;
    Tensile Strength MD 250 N/50 mm ISO 527-3;
    CD 150 N/50 mm ISO 527-3;
    Tear Strength MD 67N DIN 53 363;
    CD 93N DIN 53 363;
    Elongation MD 50% ISO 527-3;
    CD 70% ISO 527-3;
    Sealing Conditions 200 deg. C / 2 bar / 2 secs;
    Water Vapour Permeability <0.04gms / m2 / 24hrs;
    Temperature Range -40 deg. C to + 80 deg. C

    Classification

        MIL-PRF-131 J Class 1; DEF STAN 81-75-2 Type 1; TL 8135-0003

    Application

        Material has a non-woven polyester for mechanical and
        thermal protection and is recommended for use on large items
        where a robust liner is required. This information is given
        in good faith but must not be regarded as forming a
        specification.

An early instance of its use with paintings has been at the Tate
(Rica Jones) where it has been used from time to time since 1995 as
a short term, protective, lightweight, flexible backboard for
loan-in paintings and for paintings hung in difficult environments
(including one particular sea facing wall at Tate St Ives).

It is also used at the V&A (Nicola Costaras) for backing large
paintings where a backboard would be impractical, either too heavy
or too bulky, for instance where large oil on canvas paintings are
being inserted into niches in the fabric of a building or against an
outside wall.

I have also been in communication with Hugh Phibbs of the National
Gallery of Art Washington DC who uses a version of it (again mostly
for short term use for loans in and out), Mitsubishi PE/AL/PE/PET,
which is a quadruple laminate of polythene, aluminium foil,
polythene and polyester film. The polythene is used as the
thermoplastic adhesive (i.e. no additional adhesive is required). He
also uses a similar Marvelseal 360 with polyamide outer layer or
1311 with a cotton outer layer, and another called RIBS MVTR. Hugh
has carried out a considerable amount of testing and research in
connection with temporary micro-climate chambers on which he and
Mervin Richard have published, but we know of no specific
publication about this material and its longevity as yet.

Does anyone have any direct experience of this product or similar
alternatives?  Has anyone carried out tests relating to its use in
the conservation profession and particularly its longevity as a
longer term solution for the protective backing of paintings in say,
for example, a church environment? Is anyone intending to publish
any related conservation data?  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


                                  ***
                  Conservation DistList Instance 23:5
                  Distributed: Thursday, June 11, 2009
                        Message Id: cdl-23-5-018
                                  ***