From:
"dondougan@zzzzzzzz" <dondougan@zzzzzzzz>
Date:
Sun, 2 Oct 2005 18:29:23 GMT
Subject:
Project Neon and mixed media sculpture
Hi Daed (& Dulce) et al,
Quoted text begins.RE: "Pamela Soldwedel's sculptures & . . . Maybe Don Dougan knows the
answer, he uses metals a lot and he seems to know what he is doing" (per
Dulce).
End of quote.
Sorry I haven't chimed in on this topic until now, but I haven't been online in a week or so, and it will probably be another week or so until I am again.
Thanks for the kudos, Dulce, though I am not really sure about details of Soldwedel's sculptures. From the looks of it I would think she laminates the pieces, probably cutting the metal plates on the bandsaw and then grinds metal and stone to the contour. The same types of silicon-carbide abrasive disks or belts will work well on both the metal and the stone, though the metal will wear the abrasive out more quickly than the stone will so perhaps twice the quantity of abrasives will be needed for a laminated metal/stone piece than for the same form simply worked in stone.
I have laminated various materials with stone, and one thing you need to keep in mind is the varying coefficients of expansion between different materials and the adhesive. Basically, each material expands and contracts at a different rate with environmental temperature changes, and you need to allow for that in your design.
One time I laminated cast polyester resin with slate and sanded it into shape leaving the surfaces flush. However, I made the learning mistake of leaving it out in the sun while I worked on another element to the piece. A couple of hours later I went to further work the slate-resin lamination element and the resin layers had delaminated from the slate and were almost one-eighth of an inch wider than the approximately twelve-inch wide pieces of slate. When I took the piece inside out of the sun and allowed it to reach room temperature (or at least the ambient temperature of my non-airconditioned studio in the summer) the polyester shrank so as to be flush. When installed in an unheated gallery space during the following winter the polyester shrank even further so as to leave a definite recess to the touch. Though I use polyester resin adhesives to join stone to stone, I cannot recommend it to join dissimilar materials - it is simply too brittle and likely to fail as an a
dhesive in that situation.
I was able to save the piece by using a semiflexible urethane-rubber based adhesive (that is not on the market anymore) to rejoin the delaminated plastic resin and slate, and when I later sold the piece it was with the provision to the buyer that the the work needed to be kept in a stable temperature environment.
I have had similar experiences with acrylic-and-stone laminations.
In working with wood and stone the same type thing occurs, except that the major factor is humidity rather than temperature. If you work with wood at all you are probably familiar with this same issue that must be addressed in any kind of joinery working both with and across the grain (with different shrinkage and expansion factors) - mechanical joints should always be employed in addition to any adhesive joints. Plywood is much more stable than dimensional lumber, and I use it to reinforce the backsides of my thin stone wall-hung reliefs using both an adhesive (epoxy or urethane, both of which are slightly flexible when cured) in addition to mechanical pins or bolts.
I also avoid using flush contoured surfaces where dissimilar materials join, so the viewer will not easily be able to perceive any difference in expansions or contractions in the two materials.
Non-organic material pairings seem to work much better: most metal-and-stone or glass-and-stone combinations have much closer coeffiecient of expansion factors and thus usually work well if bonded with epoxies, urethanes, and silicones (this last only for elements that are relatively lightweight and have fairly large surface areas), but I still try to use mechanical joints in addtion to any adhesive joints just in case the adhesive fails.
My only exception to the rule of using a mechanical joint is when joining very small elements onto a larger piece, and even then I usually have the element fitted into a recess carved into the larger piece.
Don Dougan
http://www.dondougan.homestead.com/indexdd.html
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