molding and casting

GroopShop 2018 – Day 1

Recently we traveled to Greater Atlanta to attend this year’s gathering of the Professional Refinisher’s Group, a/k/a “Groop,” and online forum to which I have belonged for almost twenty years.  Though initially a “virtual” community, we started assembling almost annually for the past 16 years.

Our hosts this year were the cooperative known as Southern Restorations whose large enterprise is steered by Brian Webster.

Note:  If you have even a passing interest in furniture finishing or restoration, you SHOULD be a member of Groop.  For further information on joining click here.  If you attended the HO Studley exhibit in Cedar Rapids IA you undoubtedly met some of our members, as most of the docents were volunteers from Groop.

Once again GroopShop was an invigorating time of fellowship and sometimes idiosyncratic conversations ranging from surviving running a small business in an esoteric marketplace to arcane discussions of technical subjects and all points in between (virtually all the members of Groop are some version of small businesses).  I know my interest was piqued on a regular basis throughout the three days, sometimes so much I forgot to take pictures..

After opening introductions and such the first demonstration of the event was for a low-impact abrasive cleaning system that was especially appealing to our members who undertake architectural work.  Were I a younger man living near the city trying to build a business, this is a device I would certainly consider obtaining.  The results were impressive, and I brought home a cleaned table leg to see how it finishes up.

Next came an excellent presentation on recent advances in waterborne coatings systems.  While I do not use much in the way of these products, if I had a commercial refinishing shop in this age of envirohysteria, I would.

Next came Dan and Tredway demonstrating the process by which they mold and cast replicas.  I especially enjoyed this not only because I have done so much of this, but because they use a very different product line/technology than I do.  (They are Smooth-On guys and I am a Polytek guy)  Somehow I wound up with the fancy eagle, and will probably paint and gild it and perhaps put it in next year’s Groop fundraising auction.  In the mean time I will experiment with making a gelatin mold plaster cast from it.

RandyB gave another inspiring talk about life in the antiques preservation trade.  His creativity knows no bounds.  His many years of caring for collectors’ and dealers has left him with a wealth of experience and knowledge.  I first met Randy while teaching at DCTC decades ago.

BobC gave his paean to oil finishes.  Intriguing.  I think there could be an intersection between them and polissoirs.

After dinner we held our annual Refinishing Jeopardy tournament, with host MikeM invoking Sicilian rules more than once.  Like most things Sicilian it is best not to ask too much about them.  I served as the adjudicating judge for any disputed answers.  Thanks to some curious scorekeeping the hilarity was sustained to the very end.

And thus endeth Day 1.

Gelatin Molds For Plaster Casts

A couple months ago I was sent a question about using gelatin molds for casting architectural plaster.  I had seen references to the technology in several of my old books but did not possess any that provided a decent description of the material or the process, so I noodled it a bit.  I’m not an architectural historian per se, so there might be plenty of old books with the exact information.

For the past almost forty years I have relied on silicone RTV molding rubber and never saw the need to broaden that horizon, but this question prompted me to undertake some exploring.  I am awfully glad I did as I now have another potent arrow in the quiver.

Of course at issue were several considerations.

  1.  The gelatin (hide glue) would need to be used in the semi-cured state, in other words after it had gelled and had not yet lost enough water to enter the more solid phase of a dried, cured mass.
  2. The gelatin mold had to be firm/flexible enough to actually cast plaster into it, then have the casting de-molded ex poste.
  3. The mold needed to be robust enough for repeated using.  The literature references using the molds dozens or even hundreds of times.
  4. Finally, the mold needed to remain viable while not becoming a giant fur-ball of mold.

Thanks to a timely failure of a tordonshell batch I gleaned the path to success, when combining that experience with some noumena from my wanderings into materials science.  The ultimate result was a high performance molding material that was also cheap.

The trek included a number of face palm moments in discovering new ways of working.

Stay tuned.