Sio-2 · Made in Spain

Berlin Gray

cone 5–10 27 lb vacuum sealed 40% grog you cannot feel Fires cement gray

The only clay here that is not American, not Laguna, and not quite like anything else on the shelf. A gray stoneware carrying forty percent grog so fine you will never feel it, which is why it can hold fine detail and survive a bad drying week at the same time. Bare it looks like poured concrete. Under a glaze, colors do things they will not do on any other body we sell.

Berlin Gray Stoneware 27 lb vacuum sealed · cone 5–10 · in-studio pickup

What is your membership level?

$49.00 $1.81 per pound

Green level pays full price on clay.

How many bags?

In-studio pickup only. We do not ship clay. Buy it here, then show your receipt to a staff member and they will walk back with you for a fresh bag. Note that tariffs and price increases have pushed the cost of this one up a couple of dollars a bag.

A fired, unglazed Berlin Gray tile with the Sio-2 maker's mark pressed into it, showing the cement gray color and fine speckle Fired and completely unglazed. That is the actual color and surface of this clay with nothing on it, and it is the reason people fall for it.

Before you buy it

Is Berlin Gray your clay?

This is the most expensive bag we sell and the one members get most attached to. Both of those things are true for the same reason: there is nothing else like it here.

Buy it if

  • You want a piece that looks like concrete, stone or architecture rather than pottery.
  • You want your glazes to have depth and contrast without being warmed or tinted.
  • You leave work unglazed, or half unglazed. This is the clay that rewards it most.
  • You want fine detail and modeled surfaces that hold their edges.
  • You have had pieces crack while drying and you want a body that behaves itself.
  • You are making something you want people to pick up and ask about.

Buy something else if

  • You are throwing something big and tall. This one wants to sink back down on you.
  • You want pale, delicate, true-to-the-chip color. A gray ground darkens everything over it.
  • You are making a lot of pieces and price is the point. This is $21 a bag above 52 Buff.
  • You want white. It is never going to be white, or cream, or warm.
  • You are drawing detailed underglaze illustration. Do that on a light body.
  • You need it right now and every time. It is imported, so supply can be less predictable than the Laguna clays.

What it is best at

Where Berlin Gray earns its keep.

Sio-2 formulated this for artistic ceramics, and their own description is that it is ideal for throwing and modeling smooth pieces with fine details, with the high grog content giving it excellent behavior during drying and firing. In practice that combination is unusual enough to be the whole reason to own a bag.

Bare and half-bare surfaces

The best naked clay in the building and it is not close. Fired unglazed it comes out the color of cured concrete, faintly speckled, cool and matte. Half the pieces made from this bag never see a full coat of glaze.

Making glazes look expensive

Sio-2 claim the neutral base accentuates and enhances the glazes applied over it, and members here say the same thing in fewer words: colors pop on this clay. There is a full section on why below.

Fine detail and modeling

The grog in here is 0 to 0.2mm, up to 80 mesh, which is fine enough that the maker calls it impalpable. You get the structure of a heavily grogged clay with a surface that still takes a crisp line.

Surviving the drying shelf

Forty percent grog is more than most dedicated raku bodies carry. All of that pre-fired material means less movement, more paths for water and stress to escape, and a genuinely well-behaved piece on the shelf.

Functional ware

Food safe to ISO 6486, and the fired body is dense and strong. Sio-2 publish a fired bending strength for it, which no other clay we carry bothers to state.

Big, tall thrown forms

This is the honest weak spot and it surprises people given the grog content. Berlin Gray wants to sink back down while you throw big pieces. Keep it modest, or go and get B-Mix w/Grog for the tall stuff.

The nerdy part

The numbers, and what they actually mean.

This is the only clay on our shelf with a European spec sheet, and it is by some distance the most detailed one we have. Read the cone card, because where we fire it inside its range changes what you get.

Maker Sio-2, Spain Made by Ceramica Collet, who have been making clay in Spain since 1874. The only non-American clay we carry, and the reason this bag is affected by tariffs when the others are not.
Cone cone 5 to 10 A huge firing range, and we fire at the very bottom of it. That matters: Sio-2 say the grays run from cement to dark gray depending on firing temperature, so our cone 5/6 firings give you the pale cement end of that range.
Grog content 40%, impalpable The single most interesting number here. Forty percent grog, all of it 0 to 0.2mm. That is a heavily grogged clay you cannot feel, which is a combination almost nothing else manages.
Fired color Cement gray At our temperatures, a cool mid gray with a fine speckle, exactly like cured concrete. Fired hotter it goes toward dark gray, but that is not what happens in our kilns.
Shrinkage About 12% 5.7% drying plus 6.7% firing, which compounds to a little over 12% total. Those figures are measured at the top of its range, so at our cone it will move slightly less. Treat 12% as your worst case.
Porosity 0.1% at full temperature Essentially vitrified, and that figure is quoted at the top of its range. Fired at our cone 5/6 it will be a touch more open than that, which is still tight by any normal standard.
Fired strength 42.9 N/mm² Nobody else on our shelf publishes a strength figure at all. Sio-2 do, and it is high. Fifteen times stronger fired than it is bone dry.
Carbonate content 0% Zero carbonates means no lime in the body, which means no lime pops: those little craters that appear days after a firing when a speck of lime absorbs moisture and blows out through the surface.
Bag size 27 lb, vacuum sealed The only bag here that is not 25 lb, and the only one that arrives vacuum sealed rather than in a loose bag. Two extra pounds of clay for your money, which softens the price a little.

Straight answers

What is great about it, and what is not.

What it does well

  • Naked, it is the best thing in the studio.Fired with no glaze at all it looks like poured concrete: cool, matte, faintly speckled, expensive. Almost every other clay here needs a glaze to look finished. This one is finished the moment it leaves the kiln.
  • Colors genuinely pop on it.A mid gray ground is not warm like a tan clay and not blank like a white one. It gives glazes something to sit against, so blues get deeper, greens get richer and anything that pools or breaks gains contrast it would not have on white.
  • Forty percent grog you cannot feel.That is more grog than most raku clays carry, at a particle size the maker calls impalpable. You get toughness, low movement and good drying behavior without giving up a smooth surface or crisp detail.
  • It behaves on the shelf.Sio-2’s own claim is that the high grog content gives excellent behavior during drying and firing, and that matches what happens here. If you keep losing work between the wheel and the kiln, this clay removes a lot of that risk.
  • The spec sheet is a nerd’s dream.Plasticity index, carbonate content, fired bending strength, thermal coefficient. Nobody else tells you this much, and every number on it is good.
  • You get two extra pounds.27 lb rather than 25, vacuum sealed, so it arrives in better condition than a standard bag and there is more of it.

What it does badly

  • It wants to sink back down while you throw big pieces.The honest headline. For all that grog, it does not love being pulled tall, and a large form will settle on you. Keep it small to medium on the wheel and it is a delight.
  • It is the most expensive bag we sell.$49 at Green level. Tariffs and price increases have pushed it up a couple of dollars recently, and being imported means that can happen again.
  • A gray body darkens everything over it.Pale colors, pastels and delicate transparents all come out deeper and moodier than the chip. Usually an improvement. Occasionally not the piece you were picturing.
  • It contaminates other clays.Gray dust on a shared table is the fastest way to put dark spots in somebody’s porcelain or Half & Half. Wipe down after yourself. This is the clay to be the most considerate about.
  • Supply is less predictable.It crosses an ocean to get here. The Laguna clays are on a truck; this one is on a boat and a customs form.
  • It is not for underglaze illustration.Fine drawn line work on a gray body needs a white base coat first, at which point you have hidden the reason you bought the clay.
A glazed Berlin Gray bowl with blue and cream glaze running from the rim into the center Same clay, glazed. A gray body underneath gives a running glaze somewhere to land, which is why the color has depth instead of sitting flat.

Glazing it

Why colors pop on gray.

Sio-2’s own claim is that the neutral base accentuates and enhances the glazes applied over it. That is marketing language for something real, and it is worth understanding, because it is the difference between this clay and every other bag on our shelf.

The three grounds, and what each one does. A white body like Half & Half or the porcelain gives you accuracy: whatever was in the jar is what lands on the piece, cleanly and flatly. A tan body like 52 Buff or Speckled Buff gives you warmth: everything shifts toward amber and gold, and iron glazes get richer. A gray body does something different from both. It is neutral, so it does not push your color toward any hue the way tan does, and it is dark, so it adds contrast and depth the way white cannot.

The practical result is that a glaze on Berlin Gray reads as more saturated than the same glaze on white, without becoming a different color. Where a glaze thins over a rim or an edge, the gray shows through and gives you a natural dark line. Where it pools, it goes deep. Blues, greens, teals and anything with movement in it are the biggest winners.

What pops on it

Blues, greens and teals
PC Blue RutilePC Indigo FloatPC Sapphire FloatCoyote Copper BlueFloating BlueRiptideTropical Teal
The single best reason to buy this bag. Cool colors over a cool gray ground get depth without getting muddy, and the body shows through anywhere the glaze runs thin. This is the pairing members keep coming back for.
Anything that moves or breaks
Amaco PhaseCoyote FantasySpectrum FloatingMayco MudcrackSpectrum Texture
Reactive glazes need contrast to show what they are doing. On white they can look washed out and on tan they get warmed. Gray lets the movement read exactly as it is, and every break shows.
Whites and pale mattes
Coyote Gloss WhiteWhite MatteAlabasterMilk GlassGlossy Crackle White
Counterintuitive, and one of the best things you can do here. A white glaze on a gray body goes slightly gray where it thins and stays white where it is thick, which gives you shading you did not paint. On a white clay the same glaze is just flat white.
Metallics and dark glazes
PC PalladiumPC Iron LustreWrought IronBlack WalnutGun Metal Green
Dark on dark, which sounds like a mistake and is not. The transition from glaze to bare gray body is subtle rather than jarring, so a partially glazed piece reads as one object rather than two.
No glaze at all Worth listing as a glaze choice because it genuinely is one. Bare, sanded Berlin Gray beats most of what you could put on it, and it costs you nothing.

What fights it

Pastels and delicate color
Soft pinksPale yellowsBaby blues
A pale glaze over a dark body goes grayed and chalky. Not ugly, but nowhere near the jar. If you want a pastel to stay a pastel, use Half & Half or the porcelain.
Transparents and celadons
Amaco CeladonsCoyote CeladonsClear glazes
See-through by definition, so what you actually get is wet-looking gray with a hint of tint. Sometimes exactly right, especially over carving. Never the color on the chip.
Underglaze illustration
Amaco VelvetSpeedball underglaze
Colors laid straight onto a gray body come out dulled. You can lay down Velvet Ultra White first and draw on that, but then you have covered the clay you paid extra for.
Iron glazes chasing warmth
ShinosPC Ancient Jasper
These want a warm iron-bearing body to bloom against. Gray gives them contrast but not warmth, so you get depth without the golden-brown glow. For that, go to Speckled Buff.

Satin or glossy?

Both, and this is the one clay where the answer is genuinely to use them together. A matte or satin glaze sits close to the raw body in feel, so the join between glazed and unglazed almost disappears. That is how you get the concrete-and-color look this clay is known for.

Gloss is the choice when you want maximum drama: a wet, deep, saturated glaze against dry matte gray is a hard contrast and it works. Keep gloss inside anything you drink from either way, because it cleans better.

Is it beautiful naked?

This is the best bare clay we sell and it is the reason most people buy the bag. Fired unglazed it comes out looking like cured concrete: cool mid gray, matte, finely speckled. Sand it after firing and it goes smooth as polished stone. Bare clay is fine to fire here.

Half naked is where it becomes something people ask you about. Glaze the interior, leave the whole exterior raw. Or bring one glaze down from the rim and let it stop in a hard line. The contrast between a glassy pour and bare gray is the signature look of this clay. Glaze the inside of anything holding liquid, since we fire at the low end of its range and it will be slightly more open than the maker’s numbers suggest.

Combinations worth trying

One blue, poured from the rim A single moving blue brought down from the rim and allowed to stop where it stops, bare gray below it. This is the piece everyone makes with their first bag and it is popular for good reason.
White glaze, gray showing through A white gloss or matte over the whole form. It stays white where it pools and goes soft gray on every rim and edge where it thins, giving you shading for free.
Glazed inside, raw outside Wax the exterior, glaze the interior, sand the outside smooth after firing. Cheapest, fastest, best-looking thing you can do with this clay.
Carve it, then a transparent Since a clear reads as wet gray, use that. Carve or facet the leather-hard form and put a transparent over it. The glaze darkens in every cut and the whole surface looks like wet stone.
Matte black against bare body Wrought Iron or Black Walnut on part of the form, raw gray on the rest. Two dark surfaces with different textures, which is a much more sophisticated result than it sounds.
A crackle white over the top half Glossy Crackle White stopping partway down. The crackle lines pick up dark from the body beneath and the bare gray below finishes the piece.

Where these came from. The neutral-base claim is Sio-2’s own. The pairings come from the glaze makers’ layering guides and from what potters consistently report on dark and gray bodies. They are not photographs of a shelf of Berlin Gray test tiles from this studio. Fire a test tile before you commit a piece you care about, and go dig through the Glaze Bible and our glaze combination resources while you are at it.

Keeping it alive

Berlin Gray in a desert.

This bag arrives vacuum sealed with a 19% water content, which means it starts life in better shape than anything else on our shelf. Everything after you open it is on you, and Utah air is patient about waiting for a mistake.

The vacuum seal is a one-time gift

Once you cut into it, it is just clay in a bag like everything else. Close it the second you have taken what you need, squeeze the air out, and treat the rest of the block as if it were already drying, because it is.

Little specks of mold are normal

Sio-2 say so themselves: small specks of mold are completely normal in natural ceramic clays, do not affect the clay at all, and are actually a sign that it is still properly moist and soft. Wedge them in and carry on. It is an image problem, not a quality one.

Only cut off what you are using

Every cut face is a fresh surface losing water. Slice one piece, close the bag, leave the rest of the block whole rather than balling up the whole 27 pounds on day one.

Clean up after yourself

Gray clay dust on a shared table ends up as dark spots in somebody’s porcelain. This is the clay to be most careful with: wipe your table, rinse your tools, and do not roll a light slab where this one has been.

Drying it. Easier than most, and that is the grog doing its job. Forty percent pre-fired material means less movement and more escape routes for water, so this body is genuinely well behaved on the shelf. You still compress the floor and the rim, you still tent it loosely for the first day, and you still keep the wall one thickness. Those habits are cheap and they are what the clay is asking for.

When it has gone hard. Beat it. Throw the block down on the ground hard a few times, turning it between throws, or slam wedge it on the table. Grogged clay wakes up more willingly than the smooth bodies. If it is past saving on the wheel, it is still excellent slab mold clay. Never fight hard clay on the wheel. It is bad for your wrists, your hands and your back, and throwing is about touch, not strength. Full walkthrough: how to dry your pottery.

Plan it before you throw it

The Berlin Gray shrinkage calculator.

Sio-2 publish 5.7% drying shrinkage and 6.7% firing shrinkage, which compounds to a little over 12% total. Their figures are measured at the top of its firing range, hotter than we fire, so at our cone this is your worst case rather than your exact answer.

Wet measurement, in inches

Works for height, width or diameter. Measure the wet piece while it is still on the wheel or the table, before it starts drying.

Out of the kiln 4.40 in A 5 inch wet piece finishes about 4.40 inches. You lose 0.60 in.

What a bag actually buys you

Cost per piece.

This bag is 27 pounds rather than 25, so it gives you more pieces than the sticker price suggests. It is still the most expensive clay we sell, and it is still under three and a half dollars a mug.

What are you making?

These weights are studio averages for a piece thrown at a normal thickness. Heavy throwers get fewer pieces, and there is no shame in that.

Cost per finished piece $3.27 At Green level, one $49 bag makes about 15 mugs.
$49.00 One 27 lb bag at your level
15 Pieces per bag
$13.07 Clay cost for a set of four

Clay only. Glaze up-charges, kiln firing fees and your membership are separate. Leave a piece unglazed and the glaze line of that budget goes to zero, which on this clay is a genuine option rather than a compromise.

All eight, side by side

How Berlin Gray stacks up.

Prices follow the level you picked in the buy box. Tap any clay to go to its own page.

Clay Fired color Texture Best at Shrinks Price
52 Buff Warm buff tan Slightly coarse Mugs, bowls, tiles, hand building, slab molds 10% $28
B-Mix w/Grog Off white Very fine grog Beginners, joined pieces, bigger forms, and raku 11% $32
B-Mix Cream Smooth, porcelain-like Tableware, ovenware, tile, jewelry, a pleasure on the wheel 12% $36
B-Mix w/Specks Warm white, speckled Smooth Everything B-Mix does, with specks coming through the glaze 12.5% $36.50
Speckled Buff Desert tan brown, speckled Smooth, low grit Wheel throwing, warm earthy work, a reduction look in an electric kiln 12% $40
Half & Half White Smooth Large sculpture, multi-section wheel throwing, white functional ware 12% $40
#16 Porcelain Very light gray white Very smooth Fine detail, carving, slab forming, true glaze color 13.9% $44.50
Berlin GrayYou are here Cement gray to dark gray Impalpable grog Bare surfaces, glaze depth, fine detail, modeling 12% $49

Berlin Gray comes in a 27 lb vacuum sealed bag. Every other clay here is 25 lb.

After you buy it

How you actually get the bag.

Clay is not sitting out for anyone to grab. Once you have paid for it, a staff member goes and gets it with you, so you always leave with a fresh bag rather than the one that has been open on a shelf.

1

Buy it here

Pick your level, choose how many bags, and check out. The receipt lands on your phone straight away.

2

Show the receipt

Pull the receipt up on your phone and show it to any member of our staff. That is the whole check.

3

They go with you

A staff member walks back with you and hands you a fresh, still vacuum sealed bag of Berlin Gray.

Make something and leave half of it bare.

It is the most expensive bag on the shelf and the one people get attached to. Keep the form modest, put one good glaze on part of it, and let the concrete do the rest. Nothing else here looks like this.

Buy a bag See all eight clays