soapstone-msg

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soapstone-msg – 2/3/08

Use of soapstone in period. Modern sources. Carving suggestions and warnings.

NOTE: See also these files: casting-msg, plaster-msg, sculpture-msg, Relief-Carvng-art, frescoes-msg, ivory-msg, ivory-bib, pewter-msg.

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NOTICE -

This file is a collection of various messages having a common theme that I have collected from my reading of the various computer networks. Some messages date back to 1989, some may be as recent as yesterday.

This file is part of a collection of files called Stefan's Florilegium. These files are available on the Internet at: http://www.florilegium.org

I have done a limited amount of editing. Messages having to do with separate topics were sometimes split into different files and sometimes extraneous information was removed. For instance, the message IDs were removed to save space and remove clutter.

The comments made in these messages are not necessarily my viewpoints. I make no claims as to the accuracy of the information given by the individual authors.

Please respect the time and efforts of those who have written these messages. The copyright status of these messages is unclear at this time. If information is published from these messages, please give credit to the originator(s).

Thank you,

Mark S. Harris AKA: THLord Stefan li Rous

Stefan at florilegium.org

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Date: Wed, 5 Feb 1997 22:11:37 -0800

From: irgenwer at ix.netcom.com (Irgenwer Schuld)

Subject: Soapstone Casting (WAY-LONG!!!)

To: "Mark Harris" <mark_harris at quickmail>

>Greetings unto Twcs!

>>Long time no hear from! I wasn't sure you were still frequenting the

>Rialto. Got a well used saopbox around here, somewhere.

Hi Stefan:

This is the first time in a long while that I've had a little time

to spare for lurking on the bridge. I guarentee that I'll be gone

again for several months in just a few weeks. I'm on the home

stretch for finishing my dissertation research, and it manages to

eat up time very effectively! I'm also spending most of my time

"allowance" for SCA activities on running the local fighter practice

(in pursuit of my life-long ambition to become a stickjock!)

I'm crossposting this to the rialto, since you brought up a question

that more than one person may be interested in. Here goes:

>This is the first time I've heard of carving saopstone wet. No one

>suggested it here in previous discussions. In fact, some cautioned

>against getting the stone wet, because the water wood boil off and

>crack the stone similar to what you describe, even at pewter

>temperatures. >I wonder if I could bake my mold in the oven after

>carving it wet to dry it out? Perhaps nearer the boiling point of

>water than the 500 degrees of the pewter?

You basically have the right idea! I bake out my molds, first to

drive off the residual non-stoichiometric water from carving it

wet, and then to get it up to a temperature where I no loinger worry

about any sudden dehydration reactions from the hydrous silcates

present in modern soapstones.

Well - hit me over the head with a wet noodle! Shame on me for not be

sufficiently detailed. I watch the sculpture class in the room next

door to where I do most of my casting - and they're all carving their

soapstone under water in bowls and tubes, or with wetting it down with

a wet towel. I'm under the impression from talking to the sculpture

types, that this is becoming more and more common as artists get better

educated regarding the materials they use. But with regards to carving

your mold wet and then using it for casting, I need to get the

noodle squad over to do their thing to me, for I now realize that I

assumed everyone knew about how to properly bake a rock and why!

I mean - just think about this for a second - here I am, sitting around

and assuming that, of course, people bake their own rocks every day,

all the time! Why, I think nothing of popping a rock into the furnace

and cranking up the heat! YOU THINK I'M KIDDING?!?!?!?!?!?!? I'm not!

But let me explain: I torture rocks for a living. I'm a professional

mineral nerd. At this point, I probably have rocks in my head, as well

as in my lab, my office, my truck, my closet, my bookcase (well, the

nice-looking ones...). I don't think anything of just popping a rock

into the oven, if that's the appropriate thing to do!

So let me tell you in greater detail about how to bake a rock.

First, don't do it with massive talc. There's a really lovely

pale green massive talc currently on the market in the States and

Canada that I see a lot of SCA folks east of the Rockies using for

their pewter casting. But it has really serious problems with

cracking while being worked. If you put massive talc in the oven,

it's going to break! That's the nature of the mineral.

If you want to use a "soapstone" (please see my previous post for

the definition of this), use one of the schists on the market. A

phyllosilicate-rich schist that's nice enough to be used as a

soapstone has enough other stuff in it to keep it together while you

abuse it. The lovely brown-red schist from Michigan is a real winner

in this regard (give me a few days and I'll probably be able to hunt

down the quarry name); there's also a delightfull sillimanite schist

from the Ruby Mnts in Nevada that would do well for the casting

application too. The talc schist from south of Mariposa in the south

Sierra Nevada doesn't work (I tried) - it's not fine grained enough.

So the first thing you need to do is pick the right rock to bake.

Use a schist and not a one-mineral "soapstone" like sericite or

massive talc.

The second thing to do is carve it. Now, regardless of the actual

identity of the rock you're using, if it cracks while you're carving

it, it'll crack in the oven too. Rock that will crack with just little

abuse will not last through high temperature casting.

Now let's assume the mold is carved. For the sake of discussion,

I'll use a three piece mold as an exavple. For pewter casting, the

period practice (and current state of the art in SCA nations east of

the Rockies) was to pour lead pins through the mold pieces to keep

it aligned while pouring the pewter. If you're aren't familiar with

this, there are some really helpful pewter-mavins who have properly

constructed period molds and cast with them in the shopping district

at Pennsic. One of them (a laurel from Ealdemere, I believe) has a

very nice pamphlet with drawings and such - I'd go and check it out

there, since you're much closer to Pennsic than I!

Anyway, about pins: you'll need them. Melted bronze is too damn hot

to pour without pins. (If it hadn't been for the pins I had put in

my very first stone mold - the one that blew up from explosive dehy-

dration of hydrous silicate minerals - I and my casting buddy may

have ended up injured badly instead of merely embarrassed.) Now, I've

not come up with anything elegant, like the lead pins in a pewter

mold, but my current solution works well enough for me. I use bronze

machine screws and fittings - marine hardware quality bronze, in fact.

Why? Well, first, pouring bronze in a mold held together with bronze

isn't going to melt the screws and nuts. And marine bronze can

tolerate thermal expansion and contraction a lot better than most

steel hardware. Last, I lifted my marine bronze machine screws,

washers and nuts off my Dad's hoard of boat hardware so it didn't cost

me anything. The bronze screws work well with melted silver too (I've

poured silver twice now into one of my stone molds)

To put them into the mold, I drilled with my low-speed

dremel a hole just slightly smaller than the diameter of the

screw-threads. Then I carefully hand=threaded the screws into the

rock. I like a four screw arrangement best. Two screws through the

key pieces, and a screw apiece through each key piece into the base.

I do attach a nut to each

threaded screw - the thought of an uncontained steam-and-hot-metal

explosion while casting in a new mold is not a happy one. Actually

bolting the fool thing together will keep any inadvertant explosion

contained mostly within the mold itself. For metals above 1000 C,

I'm not going to trust just pins. A burn from pouring pewter can

be really really nasty - but a burn from melted bronze could ruin

the rest of your life. Bolt the mold together.

Now, after actually bolting the mold together, I retract the screws

just a little bit, so there's a small air gap between the key pieces

and the base. With all the hardware attached, and with small airgaps

between pieces, I put my new mold into my home oven, at 200 F (note

the temperature scale change here! It's important) overnight. If it

lives, I crank up the temperature to 300 F the next night, and then to

400 F. If it lives (the massive talc dies before I ever get it out

of the house, the schist survives), then I take it into the craft

center on campus and put it in one of the casting kilns - to bake at

500 C (temp scale just changed back to celsius!) overnight or until

I'm ready to cast - whichever is longer. When I'm ready to cast,

that morning I will turn up the heat so the mold will be approx 1000 C

when I have my metal melted and ready to pour. I'm estimating the

1000 C based on the color of the fire bricks on the inside of the

kiln I like best at the craft center. (After you play with melting

rocks and metals, you get a feel for temp in a furnace based on color,

instead of having to dig out the thermocouple and poking it through

the hole on top of the furnace)

This is my current procedure. It might be overkill, but the exploding

dehydrating schist made a deep impression on me the first and only

time I had a mold explode on me. And any phyllosilcate

that's been cooked a while at 1000 C is going to suffer surface

dehydration reactions and metamorphose into its anhydrous pyroxene

equivalent (in general - any rockknockers who want to pit nicks, can

do through email...). And the way to get any rock hot (not just a

phyllosilicate-rich one) is to do it gradually. Baking a rock too fast

is like microwaving cold out-of-a-can raviolli on high: it go BOOM and

make a mess!

So, to sum up in just a few words: don't use massive talc, bring your

mold up to temperature in steps gradually, and make sure your mold

achieves 1000 C before casting. And if you're not wearing a foundry

mask, hood, sleeves, mitts and attached apron (and equiv on your legs

and feet), you're going to get hurt. This is real pyrometallugy here;

dress appropriately. Paranoia is a good thing to have around the

melted "first-row" metals.

Oh, and one last thing: this isn't investment casting - so don't

throw the mold into a bucket of water to cool it down. Do that and

it will explode if it's still hot. I've seen rocks explode from

thermal stress - it's not a pretty sight, especially when you've seen

the injuries that people can get from flying hot-rock shrapnel.

What did they do in period? (I can hear someone ask!) Well, thus far

I've been able to document repeat-use molds for high-temp casting made

out of fired-clay (one mold with many pieces!, for casting multiple

bronze buckles at one shot), sericitic schist for silver jewellry

pieces, calcareous sandstone (again for bronze) and fine-grained

limestone (bronze).

There. That's all you're going to get out of me this evening!

And now it's back to procrastinating cleaning my kitchen...

ttfn, Twcs

Date: Thu, 16 Oct 1997 18:38:56 -0500

From: theodelinda at webtv.net (linda webb)

To: sca-arts at raven.cc.ukans.edu

Subject: Re: Viking scrolls--stonecarving

Soapstone is _very_ Scandinavian, and there's a reason why it's called

soapstone--it's almost that easy to carve. Quite a few of the big

artists' suppliers, like Dick Blick, sell it in small pieces for

sculpting. While it was mostly used in period for cooking vessels, why

not use it for a "personal" runestone--like an AoA scroll

Date: Mon, 20 Oct 1997 16:15:18 -0500

From: rockwallshire at webtv.net (Shared Account)

To: sca-arts at raven.cc.ukans.edu

Subject: Re: Viking scrolls--stonecarving

Re Soapstone:

Try Nasco. They sell soapstone for reasonable prices; in the 1997

catalogue, they have it listed in ranges of $1.55 for a 1-2 lb piece

through $10.20 for a 9-11 lb piece. They also carry a fun little kit

called "Rocks in a Box" for about $25; this kit contains a small stone

of amulet size, a larger stone about the size of your hand (or, at

least, the hand of a 5'8" woman), and tools needed for carving.

1-800-558-9595. I use the Ft. Atkinson warehouse (especially since,

until about a month ago, I lived within walking distance of it), but I

think you'll want the Modesto, CA warehouse. They also have a web site:

htttp://www.nascofa.com

email: info at nascofa.com

I hope this is helpful to you.

I am, your servant, Merouda, writing through the Rockwall account.

Date: Tue, 21 Oct 1997 00:38:57 -0400 (EDT)

From: DianaFiona at aol.com

To: sca-arts at raven.cc.ukans.edu

Subject: Re: Viking scrolls--stonecarving

<< >

> Soapstone is _very_ Scandinavian, and there's a reason why it's called

> soapstone--it's almost that easy to carve. <...>

Yes, but my understanding from all I have heard about it is that it is

quite expensive. Not that my project recipient isn't worth it:), but

working in expensive new materials on a wild project like this is, would

be foolish.

Does anyone have info on fairly inexpensive soapstone? We are in

Greeley, Colorado if that makes shipping or distance an issue.

Thank you,

Lughbec

Oh, the *soapstone* isn't that bad---the shipping on the other

hand......:-( Anyway the best place I know of to get it is Steatite of

Southern Oregon--not bad for you in Colorado. Unfortunately I'm in Tennessee!

You can contact them at:

(503) 479-3646 (Phone or fax)

2891 Elk Ln

Grants pass, Oregon 97527

Hope that helps.........

Ldy Diana Fiona O'Shera

Date: Thu, 6 Nov 1997 19:28:17 -0500

From: woodchucker at tbscc.com (Charles S. Myers)

To: <sca-arts at raven.cc.ukans.edu>

Subject: Re: soapstone sources?

I sculpt and have numerous art supply scources Dick Blick at 1-800-828-4548

Artfully Lidia De Algarve----------

Date: Wed, 17 Mar 1999 18:18:26 -0500

From: rmhowe <magnusm at ncsu.edu>

To: sca-arts at raven.cc.ukans.edu

Subject: Re: Soapstone

styrbjorn at juno.com wrote:

> Does anyone know where I can get relatively large chunks of soapstone? I

> want to carve some cooking vessels like the ones the Vikings used.

> Soapstone is supposed to be a natural non-stick surface. Wow, easy clean

> up at wars....

> Styrbjorn Ulfhamr

http://www.geocities.com/SoHo/Gallery/4821/CarvingPrimer/carvspsrcs.html

Magnus

Subject: Soapstone and Asebestos

Date: Sat, 01 Jan 2000 13:59:31 -0800

From: Pat Reed <preed at sos.net>

To: stefan at texas.net

Stefan:

I sent this to a couple other folks, who asked me to send it to you for

inclusion in the Florigilleum, if you think it would be valuable. You

have my permission if you choose to use it.

Patricia of Leicester

It seems I've confused everybody about soapstone and asbestos, so here's

a little more coherent information:

Soapstone is the massive form of talc, which is a metamorphic rock. If

it was a volcanic rock originally, it may have chlorite, actinolite,

epidote, and albite with it, and be converted to a greenschist.

"Granites" with a larger percentage of heavy minerals (usually dark)

will go to serpentines (a group of three minerals). If it was a

sedimentary rock, like a dirty sandstone, it will have chlorite,

muscovite (white mica), albite, and quartz with it, and form slates,

phyllites, and fine-grained schists. If it was a rock with calcium,

like a dolomite or limestone, it will have calcite, dolomite, tremolite,

phlogopite (brown mica), epidote, and quartz. Clean quartz sandstone

become quartzite, and dolomite or limestone goes to marble. The

"prolith" or original rock is put under about 2 to 8 kilobars of

pressure (about 5 to 20 kilometers depth of burial) and heated to

between 300 and 400 degrees Celcius. This can be the result of

subduction, regional metamorphism, or the emplacement of a granitic

"pluton". This is referred to as the "greenschist facies" of

metamorphism. These rocks are completely recrystallized, and usually

are well foliated. They are very, very common.

I've mentioned all of these minerals to show that "talc" is part of a

spectrum of minerals that occur together. The minerals found in an

outcrop or quarry can change over a distance of a few meters. The word

"asbestos" actually refers to the form the mineral takes naturally, like

the round "equant" shape of a natural garnet. Several types of minerals

have this characteristic hairlike, flexible form. There are five

minerals that are mined for "asbestos" used in commercial applications:

chrysotile (one of the serpentine minerals), crocidolite (an asbestos

form of riebeckite), anthophyllite (found with talc and serpentine),

actinolite-tremolite (which are closely associated with talc), and

cummingtonite-grunerite (which shows up at a higher temperature of

metamorphism than talc). The fine fibers of asbestos can be inhaled, or

get stuck in skin. The irritation this causes can lead to a variety of

diseases. The amount of exposure is the critical factor in risk

assessment. A "sanding" dust mask and goggles are absolutely necessary

when working soapstone.

So how do you know if the soapstone you're working on has any of these

asbestos minerals? You can't, because the color and hardness are very

similar in these minerals. If a you are buying from a quarry, ask them

about the mineralogy. The State's Natural Resources department will

often have that information too.

Anders, you may have had a bit of pyrophyllite in that mold that

exploded. It's associated with talc, but has more aluminum than iron.

It's white, apple-green, gray, or yellow, and softer than talc. The

name "pyro" refers to "fire" and "phyllon" means "leaf" because it falls

apart like a stack of leaves when heated. It looks more like white mica

than talc, but even my Mineralogy books say it's difficult to tell them

apart.

Notable occurrences in Norway: at Altemark, near Mo i Rana (close to a

fjord, so accessible by longship), at Framfjord in the Sognefjord area,

Otta and Kvam in Gudbrandsdalen southeast of Alesun (this is structural

quality stone),

and at Kodal (90 km south-southwest of Oslo). It also was quarried by

the Vikings on the Shetland Islands according to one reference. In

Sweden, the noted deposits are in the Garpenberg Odal field, southwest

of the Kristineberg area, and at Ravlidmgran. My email program doesn't

include Scandinavian notation, Anders, so I had to approximate the place

names.

Pat

(Geologist)

To: sca-cooks at ansteorra.org

Date: Sat, 29 Sep 2001 21:19:51 -0400

Subject: Re: [Sca-cooks] Soapstone, was: Marble slabs

From: Elizabeth A Heckert <spynnere at juno.com>

If you do a search for New World Soapstone, they have a website for

their soapstone. They are a soaptone quarry in Schuyler, VA, and their

main production is for counters and floors. We went to get tailings (I

needed loomweights) and talked to a gentleman who was making bowls out of

the stone.

Many warp-weighted looms' weights were actually broken soapstone pots.

Soapstone was a main export from Scandinavia in the Viking era

specifically for cook pots and lamps. Unlike the earthenware or clay

pots, the soapstone can come in contact with the fire.

When I went to pay for my bag o'rocks, I saw part of a price list.

Almost $30.00/square foot for counter top. The main building there

(dates from the Civil War era) was made of soapstone in the manner of the

stone fences that don't use mortar. Very cool!

Elizabeth

Date: Sun, 30 Sep 2001 23:43:08 -0500

To: sca-cooks at ansteorra.org

From: Nicolas Steenhout <vavroom at bmee.net>

Subject: Re: Re: [Sca-cooks] Marble slabs

>Where do you get your carving stone? I am having a hard time finding soapstone

>of the right softness. what I find will do, but I have hard time getting

>deatil do to crystal sizes and hardness . . . . though my molds are nigh

>inviceable :o)

I'm not Stefan, but here's where I've ordered soap stone from a couple

times.

http://www.montoyasculpture.com/Merchant2/merchant.mv?Screen=CTGY&;Store_Code=MSS&Category_Code=CSS

If that doesn't come up properly, try http://www.montoyasculpture.com

and weave your way to the soap stone section.

Muiredach mac Loloig

Rokkehealden Shire

From: val_org at hotmail.com (Gunnora Hallakarva)

Newsgroups: rec.org.sca

Subject: Re: Soapstone?

Date: 31 Dec 2001 06:09:33 -0800

>> Ralph Lindberg & Ellen Winnie wrote:

>> I suggest that you buy it from a commercial source, possibly

>> soapstone.com The reason is many soapstone deposits have asbestos. You

>> don't really want to carve stone and free asbestos fibers.

ruhl at latakia.dyndns.org (Robert A. Uhl) wrote:

> Asbestos really isn't that nasty unless you're in the asbestos

> business. Or carving it all the time. It wouldn't hurt to make a few

> carvings, but if you're going to make a habit of it I'd recommend

> against.

Soapstone typically consists of 50 to 80 percent talc (Mg3Si4O10(OH)2)

mixed with chlorite, serpentine, pyrite, quartz, calcite, magnesite,

and dolomite. Some talc *may* contain asbestos -- generally not

soapstone, nor the talc that's in almost every consumer product you

use -- but the big problem in soapstone is the talc.

Talc is carcinogenic (never mind that it's used in all cosmetics and a

staggering number of consumer products). Chronic exposure to talc dust

may result in benign or malignant pheochromocytomas of the adrenal

gland, alveolar/bronchiolar adenomas, and carcinomas of the lung. In

layman's terms, that's "lung cancer".

Talc is also a phyllosilicate, which means that breathing the dust

also puts you at risk for silicosis, a type of lung disease related to

black-lung, asbestosis, etc. Silicosis is a disabling, nonreversible

and sometimes fatal lung disease caused by overexposure to respirable

crystalline silica, such as soapstone dust. There is no cure for the

disease.

The National Institute for Occupational Safety and Health (CDC/NIOSH)

defines the REL (Recommended Exposure Limit) for soapstone at 6 mg/m3

(total dust), 3 mg/m3 (respirable).

For the official study of talc that was done to determine these

standards, see:

Toxicology and Carcinogenesis Studies of Talc

http://ntp-server.niehs.nih.gov/htdocs/LT-studies/tr421.html