Adhesive

Jane Pudsey <jane.pudsey [at] coventry__gov__uk> writes

>A literature search has identified sodium alginate as having been
>used to attach scraps to new canvas on a demounted scrap screen, but
>are unable to get hold of a sample to experiment with. Can anyone
>help, either with experience or a sample of sodium alginate, or
>other suggestions of adhesive?

You may be able to get alginate from a dentist (mine gave me some
for free) or ocular prosthetic-makers.  But I would not think it a
very good adhesive, as it shrinks enormously leaving not much in the
way of substance or filler and I think would be rather brittle in
the end.  It also would have a huge amount of water that would have
to be lost before adhesion would be effective and this would take a
lot of time.

There is a water-reversible PVA emulsion provided by Conservation
Resources, UK that might work well.  I would coat it on both sides
to be bonded, let it dry for a few minutes and then press down.  If
that has too much water in it or soaks through the canvas too much,
another possibility is the gel-like Lascaux 498-20X.  It has less
water and is an acrylic, so should be pretty stable, but can only be
reversed again with solvents.  Again, apply to both sides, wait a
few minutes and press manually.  Both of these have high flexibility
and good filling properties for uneven surfaces.  The only tricky
part is knowing how long to leave it to obtain maximum tack before
pressing together.  That will depend on temperature, relative
humidity and porosity of the substrates.  Neither has much tack at
first, but I think will work with practice.

*However*, I think it would be better to find something with no
water in it, as the lacquered paper will probably want to curl in
the wrong direction after application of a water-based adhesive. PVA
AYAF in acetone is very sticky and stays flexible, but a little hard
to spread and handle on flat surfaces in adhesive-strength viscosity
(maybe 40% would work) but, it may become acidic with aging.
Acryloid B-72 would probably work also, but it does not remain
flexible enough in my opinion.  I have used Acryloid F-10 (a butyl
acrylic)  for high-tack, flexible uses, but it is hard to prepare
unless you can get it in pellets.  My supplier provides it in a
solvent that takes too long to dry and therefore not tacky enough. I
evaporate off the solvent and re-dissolve in 111 trichloroethane.
You get immediate tack and quick drying.  Reversible in the same
solvent or mineral spirits, which is a drawback sometimes.

I hope that is helpful, or that someone else comes to your rescue,

Linda S. Roundhill
Art and Antiquities Conservation, L.L.C.
18121 157th Ave NE
Woodinville, WA 98072
425-481-0720


                                  ***
                  Conservation DistList Instance 20:13
                 Distributed: Friday, September 8, 2006
                       Message Id: cdl-20-13-003
                                  ***