You can move this picture: drag it, press and hold then drag on a touch screen, or use the arrow keys.Printable guide 04.09

The Clay Hole University Ā· Preparing Your Clay

Interesting Clay and Glaze AdditivesPrintable pottery guide

Grog, sand, paper fiber, nylon, sawdust, silicon carbide and the glaze bucket regulars: what each one really changes, how much to add, and what to clear before anything goes in a shared kiln.

$10.005 guides, 1 free
  • Skill level: Advanced
  • 20 printable pages
  • 2 video picks
  • 8-question quiz + answer key

Flip through the free sample
  • Instant download
  • Prints on any home printer
  • The full lesson stays free online
The printable, at a glance

What is the printable edition of Interesting Clay and Glaze Additives?

It is the free lesson of the same name, rebuilt as a workbook. It starts with why you would add anything to a clay that already works, then the openers (grog, sand and molochite), paper clay and why it joins bone dry to bone dry, the fibers, burnouts and curiosities, and the additives that live in the glaze bucket. Then what never goes in a shared kiln unannounced, and seven steps for mixing an additive in evenly. On paper it adds an additive log, a one-page card for the wedging table, a quiz with a full answer key, and a glossary.

Prefer to read it online first? ā€œInteresting Clay and Glaze Additivesā€ is free to read, and always will be.

  • 20printable pages, US Letter
  • 8quiz questions, with a full answer key
  • 2hand-picked videos, each with a QR code
  • 16glossary terms in plain language
  • 2workbook pages you fill in yourself
Why a printable, for this one

Two that change what you can make

People mix all sorts of things into clay and glaze, and a fair number of them get tried because somebody on the internet did.

Strip it back and two additives change what you can make: grog, which lets big work dry without tearing itself apart, and paper fiber, which lets you join dry clay to dry clay.

Everything else is standard studio chemistry or a decorative effect with a cost attached. This guide tells you which is which before you find out on a piece you care about.

Look inside

Real pages, for the wedging table

These are actual pages from the guide, shown here with the sample watermark. The full guide has none.

  • Page 5 of the ā€œInteresting Clay and Glaze Additivesā€ printable guide: grog, sand and the openers, shown with the sample watermark
    Grog, sand and the openersGrog, sand and molochite, what you gain, what you give up, and why sand is a poor choice where thermal shock matters.
  • Page 6 of the ā€œInteresting Clay and Glaze Additivesā€ printable guide: paper clay, the strange one, shown with the sample watermark
    Paper clay, the strange oneJoining bone dry to bone dry, repairing cracks in dry work, the trade-offs, and how to make it in small batches.
  • Page 8 of the ā€œInteresting Clay and Glaze Additivesā€ printable guide: not in a shared kiln, shown with the sample watermark
    Not in a shared kilnFive things to keep out of a shared kiln unannounced, from chrome that lands on other peopleā€™s work to found materials nobody can identify.
  • Page 10 of the ā€œInteresting Clay and Glaze Additivesā€ printable guide: the additive log, shown with the sample watermark
    The additive logOne row a batch: the clay and additive, the percent by dry weight, the cut face, the test tile glaze, and whether it crazed.
Flip through the free sampleTen pages, free, no email required.
Paper beats the screen here

A card for the wedging table

Additives get weighed at the scale and wedged in at the table, respirator on, not at a desk.

  • The additives card

    What the useful ones do and how much, mixing it in, the glaze bucket, and what to clear before a shared kiln, on one page.

  • An additive log

    Every batch you change, with the percentage, the cut face, and whether the test tile crazed.

  • Amounts, not guesses

    Grog at 10 to 25 percent by dry weight, paper pulp at 10 to 20 percent by volume, bentonite at 2 percent or less.

  • What went wrong, and why

    Crazing, bloating, clumps of grog, a paper clay bucket that smells appalling, and a weak fired pot.

How the guide is built

Built to test before you trust

Every guide in the series is designed as a workbook first and a document second. For this one, that means:

  • A learning dashboard before page one

    What you will learn, what you need, the traps, and what success looks like.

  • Why first, then what

    The six honest reasons to add anything, and the one reason not to.

  • The two that matter

    Grog and paper clay, each with what you gain and what you give up.

  • The glaze bucket, explained

    Bentonite, CMC gum, Epsom salts, deflocculants and frits, and what each one is for.

  • Seven steps to mix it in

    Respirator first, weigh by dry weight, slam wedge it through, then a test tile before a pot.

  • Codes that keep working

    Every QR code points at a short Clay Hole address, so a printed copy keeps working when a video moves.

Why the University is free

The lesson is free. It always will be.

All of the teaching in this guide comes from the free ā€œInteresting Clay and Glaze Additivesā€ lesson at The Clay Hole University. No paywall, no sign-up, no catch.

Commercial clay is already a blend somebody worked out carefully. Knowing the few additions worth making, and the ones to mention before a shared kiln, should not cost anybody a thing, so the lesson stays free.

The University is free and stays free. The guides are the version rebuilt for paper with an unreasonable amount of care, and buying one keeps the free side going.

Thank you. Genuinely.

Dan Pearce, founder of The Clay Hole
Collect them

Build a little pottery library

Every guide carries a permanent number. This one is 04.09, the ninth guide in Preparing Your Clay. The series is designed to live together in a binder, section by section, so the craft ends up on your shelf in the order you learn it.

Put any five printable guides in your cart and the cheapest one is on us. Put in nine and the two cheapest are on us. It happens automatically at checkout, no code to remember.

See every printable guide, or every printable we sell on one page.

  • 5guides in your cart1 on us
  • 9guides in your cart2 on us
Where this leads

From the scale to the glaze

These lessons pick up where this one leaves off. Each one is free to read now.

Good questions

Before you buy

Is this different from the free lesson?
The teaching is the same, and the free lesson is complete. The printable adds an additive log, a one-page additives card, a printed quiz with an answer key, and a glossary.
How is this different from the clay bodies guide?
The Complete Guide to Clay Bodies is about choosing a bag as it comes: the families, the spec sheet and the specialists. This one is about changing a clay yourself: what each addition does, how much to use, and how to mix it in evenly.
Will an additive change how my glaze behaves?
It can. Glaze fit depends on how the body and the glaze contract as they cool, and anything you add can change the bodyā€™s side of that. A glaze that fitted your clay may craze on the modified version, so fire a test tile before a piece you care about.
Can I just use sand instead of grog?
For opening a body, mostly, and it costs less. It is harder on your hands, and because it is silica rather than fired clay its grains expand and shrink sharply as the kiln heats and cools, so it is a poor choice where a pot has to survive sudden heating and cooling.
What does silicon carbide actually do?
It works inside the glaze layer, reacting and gassing at temperature to make craters and foam. The results can be striking, but the burst bubbles can leave razor-sharp edges, so it belongs on decorative surfaces and never on anything used for food.
Can I fire additive clay in a shared kiln?
Check with whoever runs the kiln first. Heavy organics need a slower bisque and a silicon carbide glaze is built to foam, so both change how a piece gets loaded. The guide lists five things to keep out of a shared kiln unannounced, and the one habit that makes all of them fine: tell somebody.
I am not at The Clay Hole. Is it still useful?
Yes. The materials and the chemistry are the same everywhere. Where a rule is our studioā€™s, the guide says so, and other studios set their own.
Do I need a fancy printer?
No. It is designed for an ordinary home or office printer on regular US Letter paper, with nothing important near the edges, so normal printer margins cut nothing off.
Can I print it in black and white?
Yes. Nothing depends on color, and we looked at the workbook pages in grayscale to be sure.
Can I use it on an iPad or laptop instead?
Yes. Every QR code in the guide is also a tappable link, so on a screen you just tap instead of scanning.
How do I get it after I buy?
Right after checkout you get a download link by email and on your order confirmation page. Each link works up to seven times.
What if the guide gets updated?
Every edition carries a version number. When we correct or improve a guide, everyone who bought it gets an email with the new edition at no charge.
Can I share it with my class or studio?
Please donā€™t. It is licensed for your own personal use. Anyone can read the full lesson free online, and the printable is here if they want their own copy.

Weigh it, wedge it, test a tile, and tell somebody.

Print it, keep the card by the wedging table, and log the first batch you change.

Get the printable · $10.00

The Clay Hole University Printable Guide Terms

Licensing, safety, digital delivery, and refund terms

Your copy is yours. The guide is not.

Your purchase gives one individual purchaser a limited, non-exclusive, non-transferable license for personal use only. You may download the guide to your own devices, print copies for your own use, write all over them, spill clay water on them, replace a coffee-damaged copy, and generally use the heck out of what you bought.

What you may not do is distribute the guide to anyone else, whether you charge for it or not.

That means you may not share, forward, email, upload, post, publish, copy, reproduce, resell, sublicense, redistribute, or otherwise provide the guide, or any substantial portion of it, to another person. You may not place it in a shared drive, group chat, membership library, online community, file-sharing service, studio resource folder, classroom packet, employee handbook, course, workshop, or other shared collection. You may not make copies for students, members, employees, friends, classes, studios, schools, groups, or organizations.

You may not remove or obscure copyright notices, watermarks, attribution, or other ownership information, or sell, republish, or commercially exploit modified or derivative versions of the guide.

Purchasing the guide does not transfer ownership of its copyrighted text, photographs, illustrations, graphics, layouts, worksheets, or other original content. Those rights remain with The Clay Hole and their respective rights holders. Copyright law protects the expression contained in these guides, while ideas, methods, techniques, and processes may have different legal treatment.

If you would like to use one of our guides with a class, studio, school, team, or other group, contact The Clay Hole about permission or group licensing. Please do not make twenty copies and call it manifesting.

Pottery is wonderfully unpredictable. It also carries real risk.

We work hard to make The Clay Hole University accurate, useful, practical, and ridiculously thorough. But pottery is a hands-on craft involving countless variables that no written guide can completely control or anticipate.

Depending on what you are doing, ceramics may involve extreme heat, kilns, electricity, gas, flame, sharp tools, spinning machinery, heavy equipment, pressurized equipment, silica-containing dust, fumes, chemicals, raw materials, stains, oxides, glazes, combustible materials, hot surfaces, breakable objects, and other hazards capable of causing serious injury, illness, property damage, fire, or worse.

These guides are provided for general educational and informational purposes. They are not a substitute for hands-on training, competent supervision, your studioā€™s safety procedures, applicable laws or codes, Safety Data Sheets, or the instructions and warnings supplied by the manufacturers of your clay, glaze, chemicals, tools, kilns, equipment, protective gear, or other materials.

Studios, kilns, clay bodies, glazes, firing schedules, electrical systems, ventilation systems, equipment, environmental conditions, application thicknesses, material formulations, and individual techniques vary enormously. Something that works beautifully in one situation may fail spectacularly in another. That is part of pottery. Occasionally, it is a very expensive part of pottery.

You are responsible for determining whether any technique, material, combination, firing schedule, tool, or process described in a guide is appropriate and safe for your specific circumstances before using it.

Use appropriate protective equipment. Use adequate ventilation and dust control. Read manufacturer instructions and Safety Data Sheets. Follow your studioā€™s rules. Obtain qualified instruction when a process or piece of equipment requires it. Test materials and techniques before committing important work to them. If you do not understand how to perform something safely, do not proceed until you do.

Never assume that a ceramic surface, glaze, clay body, firing method, finished vessel, repair, decoration, or other result is food-safe, microwave-safe, dishwasher-safe, oven-safe, structurally sound, chemically stable, or suitable for any particular purpose solely because it appears in or is discussed in one of our guides. Verify suitability independently when it matters.

Ceramics also refuses to sign contracts promising beautiful results. Colors change. Glazes move. Kilns have opinions. Pots crack. Materials interact unexpectedly. Manufacturers reformulate products. Equipment behaves differently. The Clay Hole does not guarantee any particular aesthetic, functional, firing, glazing, structural, or other result.

By choosing to use the information in a guide, you accept responsibility for your own materials, equipment, workspace, safety decisions, testing, methods, and results. To the fullest extent permitted by applicable law, The Clay Hole and its owners, employees, contributors, and affiliates are not responsible for injury, illness, property damage, lost work, failed projects, kiln or equipment damage, financial loss, or other loss arising from or related to your use of, or reliance upon, the guide.

Nothing in these terms excludes or limits any right or liability that applicable law does not allow us to exclude or limit.

Digital guides, immediate delivery, and refunds

These are digital products delivered electronically and made available for use immediately after purchase. Unlike a physical book, a downloaded digital file cannot meaningfully be returned to us once it has been delivered.

By completing your purchase and requesting immediate access to the guide, you consent to digital delivery beginning immediately. Where applicable law provides a cancellation or withdrawal period for digital content, you acknowledge that beginning the download, access, or delivery of the digital content may cause that cancellation or withdrawal right to end.

Once access to or delivery of the purchased digital guide has begun, the purchase is final and non-refundable except where a refund, replacement, cancellation, or other remedy is required by applicable law.

If the file you receive is corrupted, inaccessible, materially different from what was described, or there is a genuine technical problem with delivery, please contact us. We would much rather fix the problem than leave you staring angrily at a PDF that refuses to PDF.

Terms version 2026-09-19b