Acrylic paint

Gary Miller <garym [at] bbhc__org> writes

>We are about to add some color to some of the walls in our Art
>Gallery. The question has been posed as to how long a curing time is
>needed before we reinstall the paintings. ...

In the past, there was little concern or even awareness of the
content of paint and the possible effects they might have on
artefacts being displayed in close proximity to them. Today,
however, selecting a coating system for use in exhibition spaces has
become an important conservation decision. Historically, all resin
type oil and alkyd based paints, as well as water based latex paints
used petroleum or coal tar derived solvents. These solvent borne
coatings were, and are, problematic due to the high levels of VOCs
(volatile organic compounds) they give off. It is the solvents that
give paint its distinctive smell; the odour is dibutyl and diethyl
phthalate, two very volatile compounds!

VOCs are actually a class of carbon based chemicals having the
capacity to rapidly evaporate at ambient temperatures. Once airborne
they have the ability to combine either with themselves or with
other molecules to create new chemical compounds. Outdoors, VOCs
react with sunlight and fossil fuel by products that contribute to
ground level smog and ozone, in fact the EPA has determined that the
off gassing from architectural coatings is estimated to account for
about 9% of the VOC emissions from all consumer and commercial
products. Particularly harmful indoors, VOCs from solvent borne
coatings are calculated to be some ten times higher, rising to 1,000
times after the application of a new coat of paint, naturally, paint
fumes in confined interior spaces have become a serious topic.

In order to address the clean air issue, paint manufacturers such as
Benjamin Moore, Sherwin Williams and ICI, have formulated coating
systems that contain no organic or petroleum based solvents. Among
these coatings are latex water based paints with acrylic binders
(acrylic resins, polyvinyl acrylics, or a combination of both).
Essentially solvent free, they are offered as safe non toxic
products marketed as Zero VOC, Low VOC, or Odor Free paints.

However, even these paints contain some solvents as they are used as
coalescing agents to keep the binder pliable so as to form a film as
the solvent evaporates, and still other undesirable chemicals may be
added to the more complex latex formulations to help keep the solids
in suspension. It is also important to note that while some
manufacturers claim Zero VOC these paints still use colourants that
do contain VOCs, albeit in small amounts. To further complicate
matters, biocides are also added to latex paints to act as
preservatives and fungicides. Some of the biocides include arsenic
disulfide, copper, formaldehyde, phenol, and quaternary ammonium
compounds. It is also known that formulations with formaldehyde can
off gas. So even with latex paints, there are variables for VOC
exposure, though using a product with the lowest VOC level clearly
yields the smallest risk.

While early generations of solvent-free latex paints suffered from
various weaknesses, high quality latex coatings are now available.
Two categories to consider for conservation criteria are:

    1.  Low VOC Coatings: these paints, stains and varnishes use
        water as a carrier, and contain no, or at least very low
        levels, of heavy metals and formaldehyde. Though the amount
        of VOC varies among the different product offerings, EPA
        regulations affecting the use of VOC content in paints and
        stains recommend that they must not contain VOCs in excess
        of 200 grams/liter, and varnishes, VOCs in excess of 300
        grams/liter. Benjamin Moore's Pristine EcoSpec Latex and
        ICI's Ultra Hide Latex paints have some of the lowest VOCs,
        under 10 grams/liter; they are considered to be the highest
        quality paints in a ever growing lineup of products.

    2.  Zero VOC coatings: these paints are the safest for human
        health and the environment. According to EPA standards any
        paint with VOCs in the range of .5 grams/liter or less can
        be called Zero VOC. Sherwin Williams Harmony line of Zero
        VOC Low Odor latex paints and ICI Lifemaster 2000 are but
        two examples of these. The virtually odorless ICI Lifemaster
        paint's claims of a No VOC product have been substantiated
        by the Scientific Certification Systems (SCS).

the product mentioned, Regal AquaPearl Finish 310 by Benjamin Moore,
has a VOC content formulated not to exceed 250 grams/liter, and so
does not qualify either as a Low VOC or a Zero VOC coating. In its
place, you might want to consider Benjamin Moore's Pristine EcoSpec
Interior Paint System. It has a primer/sealer and four top coat
finishes: flat 212, eggshell 213, semi gloss 214, and Pearl 218.
Colours are available in white and over 1,100 custom colors, so
there should be no problem in cross-referencing the colour(s) you
have chosen.

EcoSpec is a professional quality premium interior 100% acrylic
latex system, designed for both residential and commercial spaces
where environmental concerns are a priority. The paint has virtually
no odor during application, has a very short open time, dries
rapidly, and no residual paint smells exist. Theoretically this
means spaces can be put back into use within two hours after the job
is completed. However, in practice the paint takes approximately
four days to cure and another three to four weeks before the
carboxylic acid vapours evaporate completely.

EcoSpec pearl finish is an extremely durable, washable film and no
over coating should be necessary. However, if one is desired, and to
avoid any possible problems, the top coating should be compatible
with the finish it is to go over. For this reason, it is always
prudent to use a product made by the same manufacturer, as they are
formulated to work together. Large paint manufacturers have
technical representatives who will make site visits to advice on
specifications; always we have found them exceedingly helpful.

In conclusion, to become aware of any dangerous ingredients,
Materials Safety and Data Sheets (MSDS), Technical Data Sheets (TDS)
and Product Data Sheets (PDS) can be requested from the
manufacturer(s) selected. Many have data sheets posted on their web
sites. For further information on coatings and the damage they might
cause, reference

    Coatings for Display and Storage in Museums by Jean Tetreault,
    Canadian Conservation Institute, 1999,

and

    Exhibition Case Construction Materials Note 5. 5.8 Interior
    Paints for Exhibit Cases compiled by Toby Raphael and Nancy
    Davis, April 1999. Part of the National Parks Service Technical
    Exhibit Conservation Guidelines.

Ian J. Rogan
The LV.Greyes Partnership (Conservators)
Calgary, Alberta T2T 0M4 Canada
403-228-2728
Fax: 403-228-1416


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                  Conservation DistList Instance 16:32
                 Distributed: Friday, November 8, 2002
                       Message Id: cdl-16-32-001
                                  ***