Questions and Answers
© 1988-2002 Max Krimmel, noncommercial duplication and distribution permitted and encouraged
Items in smaller type are techniques
or suppliers I don't currently use but either have used or believe to be reliable.
What is it?
Hydrated Calcium Sulfate (CaSO42H20) a crystalline form of Gypsum
Where to get it?
1. Colorado Alabaster Supply
1507 North College
Fort Collins, CO 80524
sometimes backordered 1-6 months
2. Alpine Gem and Mineral
3. Flatlanders Sculpture Supply
1193 East US 223
Blissfield MI 49228
4. Plaster City CA, just north of I-8 between San Diego and Yuma, you must contact the right person and then dig it out yourself, good price (free).
5. Rock shops along the highway, stop and ask, if they don't have it they probably know who does.
6. Contact local sculptors or sculpture supply houses, alabaster is a very popular carving stone.
7. Art supply stores, these can be expensive as they can be several buyers away from the source.
8. Look for places on the map named "Alabaster" "Gypsum" "Plasterville" etc. Gypsum is a fairly common mineral (it's the main component of sheet rock) and where there is gypsum there will be alabaster. The question is, is it solid enough and large enough to be useful?
How to cut it?
1. Hand saw, large teeth
2. Reciprocating saw, variable speed preferred, large tooth or bi-metal blade
3. Band saw, BI-metal skip tooth blade and slow speed preferred
4. Chisel and mallet, works fine but slow
5. Air chisel, works well for roughing to shape quickly but difficult to use for clean cuts
6. chain saw, it works sort of, plan on "using up" a chain and bar, keep a bucket of water handy or have a continual spray
7. circular saw, also works, use a carbide blade
8. bow saw, I use the blade with a couple of handles on it to cut the bottom of a core out of large pieces.
Just about any saw that will cut wood will cut alabaster. The problem is the quartz crystals that are in the alabaster, they take the teeth off of anything.
How do you get it on the lathe?
1. Grind a flat on what will be the base of the piece with a belt sander, glue on a pre-turned base, glue or tape a waste block to this base and screw onto a face plate.
2. Grind a flat on the rim side, glue to a face plate, turn the outside, glue on a base and waste block as in #1.
3. Pin chuck from the rim side, proceed as above. You can drill the hole for the chuck with a spade bit, but, if (when) you hit a quartz crystal that will be the end of the bit. Carbide tipped masonry bits are very available but usually require some grinding because they are designed and sized to be used in hammer drills for anchor bolts. John Nichols makes a nice pin chuck, get the smooth one, (541)449-1464.
4. It is also possible to pressure chuck a nearly finished piece. I have used this technique to finish off the base: a groove is cut into a faceplate mounted disk of plywood or particle board. This groove must fit the rim as a centering device only, do not attempt to push fit the work into it. Next, fit a piece of Styrofoam into the piece so that the pressure of the tailstock will transfer to the faceplate and not to the rim of the piece. Got that? The groove is for centering only, you can not pop fit an alabaster bowl into a groove, it is not flexible at all as wood is, any groove tight enough to hold the piece by itself is also tight enough to break it.
5. The vacuum chuck, you will need a lathe with a hollow spindle (or the Packard Woodworks adapter - 800 683-8876) a left and right hand face plate, a vacuum pump (an old refrigerator compressor will work) and an assortment of tubing, bearings, O rings, and couplings to make it work. My favorite gasket for use between the work and the faceplate is sold as a placemat. I don't know how to tell you what kind. It is about 1/16" thick, shiny slick on one side and spongy on the other. I use 3M SUPER 77 adhesive on the shiny side to attach it to the faceplate. The other side has just a bit of grip to it. Look in the TrueValue, Ace, Walmart type of stores.
A Few Words About Double Stick Tape
1. Not all tape is the same, the brand that is sold by Craft Supplies (1287 E. 1120 S., Provo, UT 84601 - 800-551-8876) works well, not all the others do.
2. Tape will creep, what you turn today may not be exactly centered tomorrow.
3. To separate the tape bond use a steady even pressure, just the sort that a heavy stone left in a horizontal position (i.e. on the lathe) will generate. Do not leave a piece on the lathe when you are not working on it.
What RPM on the lathe?
Slow! I used to rarely turn over the 220 RPM slow speed on my lathe. I have since installed a DC motor which allows me to turn as slow as about 50 RPM. On a small piece (under 6") I prefer to start at about 150 RPM and finish at about 400 RPM. DC motors and controls are readily available.
Scrapers, high speed steel works fine and gives a very smooth cut. A carbide tipped scraper lasts much longer. I sharpen my carbide tips with a 120 grit silicon carbide (greenstone) wheel. For roughing out I like to use a plunge type tool, my favorites are made by Dennis Stewart.
Many hardware stores carry a tool for cutting tile which is no more than a piece of square stock with a piece of carbide braised on to the end. These make serviceable scrapers but the stock they are made of tends to bend a lot.
Yes, alabaster sands beautifully, I start with 80 and go to 400, I use it all dry. It is easy to oversand alabaster, making the quartz and/or other harder parts of the stone stand out. Use a blueboard sanding block to keep from making waves.
Glue de jour
1. Poly Vinyl Acetate (Weldbond®) this is my current favorite (24-48 hr. dry time).
2. Hot Stuff (cyanoacrylate) OK but is rather brittle, failed joints usually leave a layer of alabaster on the wood, indicating that it is the stone itself and not the glue that is the weak link. Wipe the stone with alcohol to remove any dust before you glue it.
3. F-26, it has a good initial grab and stays flexible, allow 48 hr. dry time.
When gluing wood to stone remember that wood will move as its moisture content changes, the stone will not. After the piece is turned, finish all surfaces of the base and rim with a moisture sealing finish.
Gel Varnish I use 2-6 applications, followed by paste wax (Trewax)
Try also, paste wax alone, lacquer sealer (Deft) (Krylon Krystal Kleer) or oil (linseed, Watco, urethane etc.).
The questions you didn't know to ask
Quartz crystals are common in Colorado stone, they will take the edge right off your tool sometimes, stop and dig them out.
These are the other crystals, they are another form of gypsum and you can cut them. The problem is they usually separate from the rest of the piece, (keep filling with Hot Stuff as you turn, this will sometimes keep them in).
Yes, it is dusty, very similar to sheet rock dust, wear a mask, use a dust collector, work outside. Why does this dust seem to stick to everything? If you want to make Plaster of Paris out of gypsum you heat it up and drive out the water. The scraping action of turning creates the heat and that dust is really low grade Plaster of Paris. Water condenses on the cool cast iron surfaces of the lathe, mixes with the dust and the dust sticks. Alabaster dust is not known to be toxic. Gypsum has been in use for centuries, if the dust were toxic I think we would know so by now. You don't need to treat it like asbestos, or even cocobolo. However, too much of anything will kill you.
When alabaster gets hot the water is driven out and the stone becomes opaque. The standard for lighting fixtures is 187°, however, I think it is cumulative problem.
1. Latex or nitrile gloves, the dust can dry your skin out severely. I use lightweight nitrile gloves that I get from a janitorial supply house, they are usually blue or violet and last much longer than latex surgical style gloves.
2. Face shield, very important, these are rocks that will be flying off the lathe, not cold fettuccine.
3. Steel toes, the rocks are quite a bit heavier than wood and if you do this enough you will inevitably drop a rock off the lathe.
4. If at first you don't succeed, keep trying. In the beginning about 40% of my starts were failures, about half of those were problems with the rocks (too much quartz or structural problems) and half were just my mistakes. I am currently at about a 10% failure rate, and most of these are identified at the early stages so not much time is lost.
5. Yes, alabaster does dissolve in water. How quickly? well, a few drops of water on a waxed alabaster surface probably won't make marks. I filled a bowl with water once and found the surface to be noticeably etched half an hour later. It was as if the water just floated off the very top surface of the stone. It was easy to re-polish the piece. Obviously, if there is a fracture in the piece where water can seep through it will, and things will only get worse. One possible way to work with this is to lacquer the surface. Lacquering would work fine except for those always possible natural fractures which may cause the lacquer to check and then we're back in the same boat.
6. Have fun, this is so important that people sometimes forget that it is the ultimate point of it all.
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