Dragged plaster moldings

I beseech the many great workers of plaster for advice on this technique. I have done it before, a few years ago, and seems like I used a retarder to slow down the plaster. (In case this is not the correct term, I'm talking about scraping a profile template through wet plaster to make a moulding.)

Kevin Austin Austin Studios

Kevin Austin wrote technique. I have done it the plaster.

I use gauging plaster if I need more time.

profile template through

Advise is pretty broad. If you have any specific questions, post back.

Later,

Sorry, if that seemed vague. I thought I might avoid some pitfalls if someone had some 'never do this', or 'always do that' kind of guidlines. I need to make a 4' X 3' cove with an elliptic radius. My mold needs to be about 72' long. So I plan on filling a 4 X 3 X 72' box with #1 molding plaster (with a piece of rebar), and dragging a formica template through it. (I thought about wrapping some burlap or fiber around the rebar, but I'm afraid of running into it with the template.)

Should I mist the plaster when I get close to get a smoother surface?

In the past, for a short run like this, I would mill the reverse in wood, and make a more permanent mold, but I'd like to broaden my horizons a little.

Thanks,

Tom Battersby is right, this is difficult to explain in a few short words. You are describing 'plasticity' which has many stages, all of which are used or can be used in running cornices or reverse molds. For run in place work, the plaster is mixed with lime putty. For bench work, gauging plaster would be a good choice but, believe it or not, not available in Canada. If this is going to be a high quality model to take a mold from, or a pattern for composite or vacuum forming, try Hydrocal B111, it has a longer plastic period than normal hydrocal and can take a high polish and hard use. Probably a special order for two or three bags. Build up a backing section with cheaper plaster (No 1 Casting Plaster is the lowest cost alternative to hydrocal) and burlap, before you use the more costly Hydrocal.

Once plasticity is out of the way, then you have to make the tools. Is it worth all the trouble to learn all these skills -you bet! If you have any sense of proportion and perspective your custom moldings can make a room sing and soar. Storebought moldings are never accurate to a specific room and it shows, its like buying a poorly made suit from a catalog versus a tailored item from a master. Yes the cost is more- but this is a room that should have been designed to last 100 years, and if made properly, will always be a special place - the artwork and furnishings may change but the room will be permanent. Three coat traditional veneer plaster walls absorb all the sound, absorb carbon dioxide, are absolutely fire proof, bug proof and mouse proof. The walls can be be tinted on the final coat for a fresco effect which the painters have a less beautiful version called 'Venetian Plaster', the walls are then sealed with scented beeswax and lightly polished. This a room which is now a piece of art and has a magic quality which people cannot quite identify.

Unfortunately though, a lost and dying art, and it is an art - be sure of that. Plasterers or stuccotari are no longer considered artists and the trade itself has much to blame for its decline.

Kevin Austin wrote

Never show fear, or that plaster *will* kick your ass.

Always take the bull by the horns.

I suspect you are making a mold for casting urethane. Your intent is still a little vague. If so, the plaster will remain in the box. Right? In that case, rebar and burlap, or sisal, is unnecessary.

You can run that piece with pure moulding, but, for one of that size, I would recommend a blend of USG #1 Premier Moulding, USG Gauging (slow set), and Ivory Finish Lime.

Yes. Mist it fairly heavily, or, I drip water on the face with my brush. If I have a tender along, he, or she, will do the dripping immediately before the final pass or two. An assistant makes the work much easier. Don't screw around. Once you get started, you gotta move. Be prepared, have everything at arms length, and get finished. Executed properly, your finished product should be so smooth it'll make a babies butt feel like 60 grit floor sanding paper.

wood, and make a more

If you would be a little more specific in your description, and intentions, I would elaborate more on the subject.

Later,

The way that I would do this is to attach your sheet metal template to a horse and ellipse trammel set up on a greased plaster bench (mine is 11 foot by 7 foot). Hammer in small headless nails/brads along the track of the ellipse, start building up runs of plaster, careful with chatters caused by swelling plaster, always leave enough room so your final run is minimum thickness. The final run is creamy plaster, there will be quite a bit of suction caused by the already set plaster. The molding then lifts off the nails. It must be cured in warm air. You should be able to easily produce 5 moldings in one day from the one trammel and mold.

This type of work is easier to do in place with lime putty and plaster, or lime putty and white cement, - just my opinion and I do not know the circumstance.

Both of these techniques are considered advanced plaster techniques and there are very few people available who can do this work with any confidence. Ironically they are very fast, and involve a minimum of equipment and materials. Setting up a router and/or table for an ellipse and multiple passes is also not easy. To my eye, milled moldings are too sharp, too perfect, too distracting. Your box technique is much the same as reverse run moldings for which English and Irish plasterers are most well known. I assume the side of box would be routed to the profile of the ellipse? The challenge is/was to be able to make these reverse molds in pieces, to accomodate undercuts. Sadly, the work of ghosts long gone.

someone had some 'never to be about 72' long. So of rebar), and dragging a fiber around the rebar, but wood, and make a more

Gary Waller wrote

Gary, what kind of trammel do you have??

You can't knock off at noon Gary, you need to put in your eight.

From my perspective, here in South Texas, the trade is not the blame. In the early 70s the federal gov't passed the so called 'right to work law'. At that time the Operative Plasterers and Cement Masons Union, Local #178, lost all control over quality. Prior to this time, to get your card, a four year apprenticeship was a requirement. Undesirable work earned a fine and/or suspension. Post RTW law, every swimming pool jockey in SATx was allowed on the job and had to be paid scale. In most cases, a blind Arctic Hare, running on his back legs, with a broken cedar shake in his ayehole, would turn out a finer product. As a necessity of survival, corners had to be cut, and one by one, each and every shop sold out and shut down. Over the last 25 years the decline in quality has progressed to a point of no return.

From what I see it is not a question of being *able* to 'afford the real thing'. 99 times out of 100, the first thing I hear is 'We're working on a budget'. The second thing is 'We're behind schedule'. So, I go for the one out of a hundred, and let the other 99 roast.

Almost all of the plasterers and stuccoists that I grew up with are dead and gone. My name is coming up on that list pretty soon. My name is already on my tombstone, the plot is waiting. All they have to do is engrave the date of death, and that's already paid for. I'll just ride it out from here on.

Tried to save the trees Bought a plastic bag The bottom fell out It was a piece of crap

Saw it on the tube Bought it on the phone Now you're home alone It's a piece of crap

I tried to plug it in I tried to turn it on When I got it home It was a piece of crap

Got it from a friend On him you can depend I found out in the end It was a piece of crap

I'm trying to save the trees I saw it on TV They cut the forest down To build a piece of crap

I went back to the store They gave me four more The guy told me at the door It's a piece of crap

Neil Young, from 'Sleeps With Angels', 1994

Later,

Thanks Gary & Tom, Very helpful!! I'll be more specific next time. BTW is it frowned upon to send jpegs along with posts, to better communicate a point? Ive only seen it a few times in this newsgroup.

along with posts, to

Kevin, I believe it's best to put the images on your webpage somewhere and post a link here.

Be sure to get some pix of your finished product (or further questions), and post back here with a link to the location.

And, by the way, what is the cove mold with the constantly changing radius, for??

Good luck with your horizon broadening,

I used to use 3/4' channel iron set up as slides, but now have routed out slider channels on a thick piece of UHMW polyethelene, (as used for cutting boards) it is slick and true and cheap. Don't get to use it very often.

Didn/t want to brag Tom, plus my superhuman skills have been downgraded to merely omnipotent.

I see it more of a question of not knowing the material. I compare it to cheese. If all you know is processed slices, there is no point in me talking of the finer cheeses of the world. You have to taste for yourself, and even then, many flavors are an acquired taste. The architects and designers little understand the world of fine painting, bronze/stone sculpture and plaster (modeled and molded stucco), they are very defensive of their position and rather than say they don't know a lot about 'xxx', they would rather say that 'xxx' is too expensive. Fine plasterwork then comes to live in the world of those who have made the effort to appreciate fine art, fine painting and fine cheese - when discovered it is a heavenly joy - the other mortals stick with sprayable cheese on crackers. I mean after all, who would pay $10 for a pound of dried milk that smells like old socks. Flavors and tastes have been so manipulated, synthesized and advertised that when real blueberries were finally introduced to Japan, the consumers revolted - in no way did these little berries taste like blueberries, what were the importers trying to pull off?

Jeez Tom you're scaring me! I better get to work producing those photos and articles pronto.

Gary Waller wrote

Seems like that would work smoother than the one I built (welded up out of plate and flat strap).

I built mine about twelve years ago for a specific project, and it's only been used three or four times since.

Well put Gary.