Glaze Testing Guide: Test Tiles, Sieving & Specific Gravity

Those tiny white specks on your fired bowl are not a kiln mystery. They are material lumps a 100 mesh sieve removes in about two minutes.

This glaze testing guide covers the three habits that make fired results repeatable: making consistent test tiles, wet sieving every batch you mix, and measuring specific gravity before you dip. You get working mesh numbers, dip targets by application, and a water correction table by the gallon. Frequent problems like specks, crawling, and bucket hard pan get direct fixes later in the post.

What Is Glaze Testing and Why Does It Matter?

Glaze testing runs every recipe and every bucket through three controls: a consistent test tile, a sieved slurry, and a measured specific gravity. Skip one control and your fired surface drifts batch to batch, even when the recipe never changed.

Each control answers one question. The tile proves what the recipe does on your real clay body, the sieve removes every agglomerate the mixer missed, and the specific gravity number controls how thick a dip deposits.

Dry glaze materials do not dissolve in water. They hang in suspension, and fine powders cling together into agglomerates, meaning clumps of particles stuck together in the mix.

Fire an unsieved batch and those clumps melt into specks, pinholes, and streaks on an otherwise correct recipe. The recipe was never the problem; the preparation was.

In Mastering Cone 6 Glazes (2002), John Hesselberth and Ron Roy argue that durable, well fitting glazes come from documented, repeatable tests rather than luck. Their line blend method turns guesswork into data you can read five batches later.

The economics reward the discipline. A 100 gram test batch costs one to two dollars in raw materials, and one kiln run can answer questions for ten recipes at once.

Control the tile, the sieve, and the number, and your kiln stops surprising you. That control starts with five cheap tools.

What Goes Into a Complete Glaze Testing Toolkit?

A complete glaze testing kit costs under $100. The five core tools: an 8 inch stainless test sieve, a drill mixer attachment, a glaze hydrometer, a 0.1 gram scale, and a true 100 milliliter container.

Everything else, buckets, wire racks, and stir sticks, you probably already own. Buy these five once and every test you run for years rides on them.

The Sieve, the Mixer, and the Hydrometer

Sieving is a type of wet processing, meaning the glaze passes through the mesh as liquid slurry rather than dry powder. Wet processing is the studio default because wet silica stays out of the air you breathe.

The workhorse is a full height 8 inch stainless steel test sieve in 80 and 100 mesh, held over the bucket. A stainless mixer attachment on a drill breaks the settled layer at the bucket bottom before the sieve ever sees the glaze.

Key Specifications:

• Frame diameter: 8 inches (20 cm), fits a standard bucket rim
• Most used mesh counts: 60, 80, 100, 120
• 100 mesh opening: 150 microns (0.0059 inch)
• Typical price: $18 to $40 stainless, $10 to $15 nylon

A glaze hydrometer gives you a thirty second check on big dipping buckets. Keep the scale method, covered two sections down, for record grade numbers on small test batches.

Key Specifications:

• Scale range: 1.000 to 2.000 specific gravity
• Depth required: about 8 inches (20 cm) of stirred glaze
• Typical price: $10 to $30

The Scale and a True 100 Milliliter Container

Record grade specific gravity readings come down to two tools: a 0.1 gram digital scale and a container that truly holds 100 ml. The Digitalfire reference library, built by materials engineer Tony Hansen, recommends this weighing method as the more reliable way to track a glaze.

Key Specifications:

• Capacity and resolution: 500 g at 0.1 g
• Price: $12 to $25
• Also handles: weighing 100 gram dry test batches

Tapered bucket markings lie, because they measure height rather than true volume. A straight sided glass graduated cylinder with one verified 100 ml line keeps the math honest.

Verify any container once by filling it to its line with water. If the scale reads 100 grams, the mark is true forever.

Safety Gear: Treat Silica With Respect

Glaze powders contain crystalline silica, and particles under 10 microns reach deep lung tissue where they cause scarring, the disease called silicosis. The 2016 OSHA respirable silica standard caps workplace exposure at 50 micrograms per cubic meter over an eight hour shift, a vanishingly small amount.

Wet work first: wet sieving, wet mopping, and a box of nitrile gloves cover most of the daily risk. Use a NIOSH approved respirator with P100 cartridges for any dry material pour. A wet mop or HEPA vacuum cleans up; a dry broom puts silica back into the air.

One full height stainless sieve and one good scale are the only purchases you cannot work around. Everything else has a budget workaround.

How Do You Make Glaze Test Tiles?

Make test tiles from your production clay body at a consistent 1/4 inch (6 mm) thickness. Cut 2 by 4 inch (5 by 10 cm) strips, stamp a code, dry flat, and bisque them beside your normal pots.

A test tile is a small slab of your real clay body, so it shares the absorption and thermal expansion of the work you actually make. A tile that matches reads true; a tile from a stray bag reads fiction.

Start with a cone 6 stoneware clay if mid fire is your range. Cutting tiles from a random scrap body produces a confident, wrong answer about glaze fit.

Key Specifications:

• Firing range: cone 6 (2232°F, 1222°C) for a typical mid fire body
• Shrinkage: about 12 percent from wet to fired
• Absorption at maturity: roughly 2 percent
• Cost: $18 to $25 per 25 pound bag

The stepper below compresses the whole forming process into seven steps you can run from the clay bag to the bisque kiln.

Why Tile Shape Changes What You Learn

A flat stick tile answers color and texture questions. A curved tile hung vertically answers flow questions, because the dip at the curve shows exactly where a glaze breaks over edges and how far it runs.

Texture testing needs one more wrinkle. A thumb groove or a scraped band on the wet tile shows how glaze pools over relief, and that pooling behavior is what most mugs, bowls, and rims depend on.

Rolling, Cutting, and Stamping Your Tiles

Roll between two parallel slats or use a rolling pin with thickness rings so every slab lands close to 1/4 inch (6 mm). Cut the strips with a needle tool and keep the offcuts as small color chips.

Stamp each tile at the leather hard stage with a metal number and letter stamp set. A stamped code reads after ten cone 10 (2345°F, 1285°C) fires, while pencil and marker fade on a wet dip.

Punch the hanging hole now or never. Drilling a bisqued tile chips the edges and starts cracks that survive glaze firing.

Drying and Bisque Firing the Tiles

Dry tiles flat under loose plastic for the first 24 hours, then open air for another 24 to 48 hours so both faces dry at the same rate. Uneven drying is what warps a thin slab, and a warped tile turns a good run into a misread.

Bisque is the first firing, the one that turns bone dry clay into porous ceramic. Run the tiles on your normal cone 04 (1945°F, 1063°C) schedule with your pots, because a solo fast firing answers nothing about production reality.

Place an Orton witness cone on every shelf level. Heat work, the combined dose of temperature and time that matures glaze, is separate from what the controller display reads, and the cone is the part that tells the truth.

Key Specifications:

• Forms: self supporting cones or set bar cones with a cone holder
• Placement: one cone per shelf level, front and back on big loads
• Reference: cone 6 equals 2232°F (1222°C) at a 270°F (150°C) per hour ramp

A hundred matching bisqued tiles make every future batch prove itself under identical conditions. What you pour onto those tiles has to earn the same trust.

Why Does Sieving Change Fired Results?

Sieving removes the clumps a drill mixer cannot break: agglomerated colorant balls, gelled clay, dried bits from bucket walls, and stray debris. The fired difference is instant, a smooth transparent surface versus specks and streaks from an identical recipe.

Glaze chemistry looks uniform in the bucket, but the particles say otherwise. Red iron oxide and copper carbonate are the famous offenders, balling into agglomerates that ride through mixing untouched.

Those intact balls melt from the outside during firing. The result is a dark center, a raised speck, or a pinhole where gases pushed through the glass.

The condition that triggers the behavior is simple: any solid lump larger than the mesh opening survives. Mesh count is the number of wires per inch of screen, so 100 mesh, with 150 micron openings, screens far finer than 60 mesh at 250 microns.

The Digitalfire reference library treats 80 mesh as a sensible production standard for most stoneware glazes, with finer passes reserved for engobes and fine slips. If the batch passes the mixer and still shows heavy residue, the mixing step failed, not the glaze.

In plain terms: the mixer blends, the sieve verifies, and anything the mixer missed gets caught at the mesh instead of on a finished pot.

Use the table below to match mesh count to the job before you buy a sieve or pour a bucket.

Mesh count	Opening (microns)	Opening (inches)	Best studio use	Trade off
40	425	0.0167	Screening reclaimed slip before pugging	Far too coarse for any glaze
60	250	0.0098	First pass on heavy, clay rich mixes	Still passes speck forming lumps
80	180	0.0071	Standard production pass, most stoneware glazes	Fine specks can still pass
100	150	0.0059	Standard for dipping, brushing, and spray glazes	Slower with viscous slips
120	125	0.0049	Engobes and fine liner glazes	Blinds fast under pressure
150	106	0.0042	Underglaze and very fine slip work	Slow, short sieve life
200	75	0.0030	Stain washes and lab grade fining only	Clogs almost immediately on glaze

Openings follow the US standard sieve series, ASTM E11 designations. For most home and school studios, the 100 mesh row is the single sieve that covers every glaze job on this list.

The residue on the mesh is a free batch report. A spoonful of soft lumps means your mixing fell short, and pebbles or plaster chips mean contamination that no recipe change can rescue.

A 100 mesh pass costs minutes and removes the most common reason potters blame a good glaze for a bad bucket.

How Do You Wet Sieve a Glaze Batch?

Wet sieving takes 5 to 10 minutes with three tools: a drill mixer, an 80 or 100 mesh sieve, and a stiff rubber rib. Mix the bucket completely first, then pour it through the mesh into a clean second bucket.

Two habits do most of the work here. Mix before you sieve, and never work the mesh dry.

The stepper below lays out the full sequence for one five gallon bucket from settled sludge to pourable glaze.

Working the Mesh the Right Way

Light pressure in slow circles passes glaze. Streaking or a puddle that refuses to drain means the mesh is blinding, meaning the openings have packed with solids, so ease up and let the rib do the work.

Use a stiff rubber rib or the flat of a dedicated sieve brush. Never attack the screen with metal tools, which slice mesh apart one pass at a time.

Reading the Residue Like a Batch Report

Soft lumps that smear mean the mixing step fell short, so re-mix the bucket, not just the sieve load. Hard chunks and plaster mean incoming contamination, and they go in the trash along with a careful hunt for the source.

The classic red smear is red iron oxide, the most famous agglomerate in the studio. Copper carbonate behaves the same way, so any dry powder residue earns a second 100 mesh pass, not a shrug.

Digitalfire documents the same failure: undispersed oxide lumps that pass drill mixing and surface later as fired specks. In plain terms, if the residue looks like pigment rather than dust, the batch is not done.

Preventing Cross Contamination Between Batches

Cobalt stains powerfully at a fraction of one percent, so residue from one dark blue batch can tint your white glaze for weeks. Dedicate sieves per color family when benches allow, and rinse hot with a final clean water pass when they do not.

Verify cleanliness with plain water. Pour a cup through the washed screen and check the catch bucket for color; any tint means pigment is still hiding in the mesh.

The sieve is the cheapest inspection point in the studio, because residue you can see never ends up on a pot. The number that comes next, specific gravity, is what keeps the coat on that pot consistent.

What Is Specific Gravity and Why Does It Control Results?

Specific gravity is the weight of your glaze slurry compared to the same volume of water, and water defines 1.00. A dipping glaze works best between roughly 1.45 and 1.55, so a 100 ml sample should weigh about 145 to 155 grams.

The number matters because it tracks solids loading, the amount of dry material in each fluid ounce. More dry material per dip means a thicker melted glass layer, and glass depth drives color saturation, run risk, and flaw behavior.

Too high and crawling, where the glaze pulls apart into bare patches, becomes likely because a thick coat shrinks more while it dries. Too low and colors wash out into weak, under covered surfaces.

In plain terms: heavier glaze leaves a thicker coat, and the thickness sets almost everything you see after firing.

Commercial dipping glaze instructions commonly set dip targets in that 1.45 to 1.55 window, and buckets beyond 1.60 or under 1.40 misbehave fast. Brushing lines ship much thinner, near 1.15 to 1.30, because gum binders perform with extra water.

Mayco and Amaco brushing instructions both direct users to stir fully rather than add water, and that guidance is worth following. Brushing products engineered at their shipped thinness rarely forgive adjusted specific gravity.

Lines like Amaco Potter’s Choice cover the cone 5 to 6 (2167 to 2232°F, 1186 to 1222°C) range in brushing form. Check each jar for its own AP or CL seal, because seals vary within a single product line.

Key Specifications:

• Firing range: cone 5 to 6 (2167 to 2232°F, 1186 to 1222°C)
• Application: two to three brushing coats
• Adjustment policy: stir only, no thinning
• Common sizes: pint to gallon

Potters who start with commercial glazes can compare prices across a roundup of dependable online glaze shops before committing to a full line. Testing any commercial glaze on your own tile still matters, because fit and color only mean something on your body at your cone.

Measure at room temperature, about 68°F (20°C), the reference point manufacturers use. A bucket in a 90°F garage reads slightly lower than the same glaze in a cool basement, so note your studio conditions when you compare long term logs.

One number, taken the same way every time, predicts how every glaze in the studio will behave on the next dip. Taking it consistently is the whole game, and two methods get you there.

How Do You Measure Specific Gravity?

Measure specific gravity two ways: float a glaze hydrometer in a freshly stirred bucket, or weigh exactly 100 ml of stirred glaze on a 0.1 gram scale. A sample weighing 148 grams reads 1.48, and that one division is the entire weighing method.

Method One: Reading a Glaze Hydrometer

Stir the bucket fully before every reading, because solids settle within minutes and the top layer thins as they drop. Spin the hydrometer as you release it so it floats free, then read the scale at the liquid line, the curve called the meniscus.

Depth is the hydrometer’s demand. The spindle needs about 8 inches (20 cm) of glaze to float clear of the bucket bottom, so small test batches cannot host it at all.

Method Two: Weighing 100 Milliliters on a Scale

Tare your container, fill to the verified 100 ml line with well stirred glaze, and read the grams straight off the display. Record grade results come from two habits: verify the container once with 100 grams of water, and log every reading beside the tile code.

Digitalfire, Tony Hansen’s reference library, recommends this fixed volume weighing method as the more reliable of the two. The scale reads the number, not your eye at the waterline.

The table below lays out how the two methods trade speed for precision so you can stock the right one for each job.

Most studios end up owning both. The hydrometer lives in the production dipping bucket and the scale method runs every test batch, and together they cross check each other nicely.

The discipline stays the same either way: stir, measure, log, and only then adjust, which is exactly what the next section covers.

How Do You Fix a Specific Gravity Reading That Is Too High or Too Low?

Bring a high reading down with water: about 75 to 85 ml (2.5 to 3 fluid ounces) per gallon moves the number about 0.01. Raise a low reading by settling the bucket overnight and pouring off the clear water on top.

Stir for a full two minutes after any water addition before you re-measure. Dry materials need that minute or two to absorb and distribute, and an instant recheck reads falsely thin.

Worked example: a one gallon dipping bucket that evaporated from 1.50 up to 1.56 needs about 15 fluid ounces (450 ml) of water. Add half, stir two minutes, re-measure, then finish the dose if the number still sits high.

Overshooting has no quick fix, so dose in halves. A thinned bucket requires pouring off water after overnight settling, and that waiting period costs a whole studio day.

Raising the number has two clean routes. Evaporation with the lid off overnight moves a bucket up a few points, or adding dry glaze powder works when you re-sieve the batch at its standard mesh afterward.

Commercial brushing glazes are the exception that proves the rule: their makers ship them ready to stir, and any error belongs in the trash, not the bucket. Digitalfire makes the same point about discipline over improvisation: remeasure, record, and let the log hold the corrections.

Every correction belongs in the log, because a corrected bucket that goes unrecorded repeats its drifting mistakes the next time you mix the recipe.

How Do You Record Tests and Build a Glaze Library?

Attach three numbers to every fired tile before it enters storage: the recipe code, the specific gravity of the dip, and the verified firing cone. Those three data points rebuild an entire result years later without guesswork.

The Complete Guide to Mid-Range Glazes (2014) by John Britt builds its whole system on labeled tiles and repeatable notes. The habit is identical in every serious studio: file tiles by cone and recipe family, and let the stamps carry the memory.

A Standard Dip and a Thickness Ladder

Dip each tile for a slow count of three, straight down and straight up, with fingers on clean spots. Consistency beats care here, because one lazy extra second in the bucket changes coat thickness more than most mixing errors.

Build a thickness ladder on the same tile. Let half the tile dry and dip it a second time, then look for the application where color saturates without crawling or running at the edges.

Reading Tiles After the Firing

Inspect fired tiles in daylight and record three checks: crazing, color streaking, and how the glaze broke over the curve. Crazing is hairline cracking in the fired glaze layer, and a felt marker test finds it instantly.

Wipe the marker after a minute. Ink that stays behind in fine lines marks crazing too small for the eye, which matters before any glaze goes on functional ware.

Film each finished tile set next to a code card while it sits on the shelf. A photo log paired with stamped tiles creates a searchable record that outlives any notebook and travels with you between studios.

The same slab and glaze habits behind test tiles scale up fast, and potters who catch a taste for flat work can move straight into planning larger decorative tile projects with the identical skills.

Three numbers on every tile turn a box of fired strips into a working database. When a fired answer still looks wrong, the troubleshooting map below starts with the failure every potter meets first.

What Can Go Wrong, and How Do You Fix It?

Five problems explain most failed glaze tests: specks, crawling, pinholes, crazing, and a bucket settling into a hard pan. Each traces back to a condition you control with the sieve, the specific gravity number, or the firing, and each has a fix that fits one studio session.

Specks and lumps in the fired surface. The mechanism is intact agglomerates that reached the pot through a coarse or torn sieve, often mixed with dried glaze sloughed off bucket walls. Hold your sieve to the light before use, because a torn patch passes debris until you replace the mesh.

Fix it by re-sieving the strained batch at 100 mesh and wiping bucket walls with a damp sponge each session. If residue appears every pass, buy a new sieve before blaming the recipe.

Crawling, the glaze pulling into bare patches. Crawling fires when the wet coat shrinks too much during drying, so dust on the bisque or overthick application from a high specific gravity causes most cases. Recipes with very high clay content crawl more on smooth bodies, and that failure mode runs in the recipe itself.

Fix it by rinsing tiles or ware with clean water before glazing, then dropping the batch about 0.05 with the water table above. A second test tile confirms the fix before a whole kiln load rides on it.

Pinholes peppering the surface. Pinholes come from gases that escape through a thick film faster than the melt can heal over them, from dusty application surfaces, or from organic burnout trapped in a rushed schedule. The failure shows up as tiny craters rather than the larger blisters of a severe case.

Fix it in three moves: dip one coat thinner, wipe surfaces with a damp sponge before glazing, and slow the last 200°F of the glaze firing so the surface has time to smooth.

Crazing, those hairline cracks in the glaze. Daniel Rhodes, in Clay and Glazes for the Potter, revised edition (2000), frames the cause: the glaze contracts more than the clay body on cooling, so a mismatch in thermal expansion produces the cracks.

Fix it by adding silica to the recipe in 5 percent steps, firing a fresh test tile after each step, and verifying the actual cone with witness cones so heat work variables stay controlled.

Hard pan, the packed layer at the bucket bottom. Fine particles compact and gel over days until no stir stick reaches the bottom, resulting from a suspension failure, glazes lacking binder, infrequent stirring, or excess water. The condition is simply time plus settling, and every bucket headed there shows an early sign: a clear water layer on top.

Fix it with daily stirring, about 2 percent bentonite blended into a recipe you mix yourself, or a tablespoon of saturated Epsom salt water per gallon gelled into the batch to hold particles in suspension. Digitalfire documents this flocculation approach as standard practice, so re-check specific gravity after any additive.

Functional ware carries one more rule: a crazed surface, however lovely, is not a sanitary food surface, because hairline gaps hold bacteria that no dishwasher reaches. Before any glazed work serves food, make lead verification part of the process, and checking fired glaze for lead before food use covers both home swabs and lab options.

Nearly every defect on a test tile traces back to three dials you already own: slurry uniformity, coat thickness, and glaze to body fit.

Frequently Asked Questions About Glaze Testing

Can You Skip Sieving a Brand New Commercial Glaze?

You can skip the first dip with a fresh commercial glaze, because the maker sieved it before it shipped. After months of settling, a formed hard pan, or any speck appearing on a fired test tile, an 80 or 100 mesh pass costs minutes and settles the question permanently.

Settled and re-wetted glaze re-forms lumps from material that packed at the bottom. The residue you see during a sieve pass is a direct report.

Make the call with a test tile, not with a guess on a finished bowl.

Can You Use a Kitchen Strainer Instead of a Test Sieve?

You cannot for glaze work, because a kitchen colander passes debris in the 2 to 3 millimeter range while the studio standard sits at 150 microns, the 100 mesh opening. A dedicated stainless test sieve runs $18 to $40 and keeps kitchen tools away from studio chemistry.

Fine tea strainers approach 60 mesh, but they are uncalibrated, sag under load, and still leave the specks that show at cone. Cross use also drags glaze chemistry into the kitchen.

Buy one dedicated sieve and retire the kitchen hardware from glaze duty.

Do You Need to Measure Specific Gravity for Brushing Glazes?

You do not need to measure commercial brushing glazes for daily use, because they ship engineered at their working thinness near 1.15 to 1.30 and the makers instruct users to stir rather than thin. Measure only when results drift, such as weak color after you added water or patchy coverage after a lid sat loose.

Take one baseline reading from a brand new bottle and write it on the label. A later reading against that baseline tells you exactly how far the bucket has drifted.

Start the habit with your next fresh jar before any water touches it.

Why Did My Bisque Test Tiles Warp?

Warp comes from drying stress, not from the bisque itself, because a 1/4 inch (6 mm) slab cups when one face dries faster than the other. Kiln placement adds fuel, since tiles at the shelf edge on a fast ramp heat unevenly on their faces.

Keep tiles flat under loose plastic for the first 24 hours, then finish drying on an open rack.(Stack flat with weight centered, and the problem disappears in the next batch.)

Dry the next batch on a wire rack away from drafts, and warping leaves your readings for good.

Why Does the Hydrometer Give a Different Number Each Time?

The glaze changed between readings, because solids settle within minutes and the top layer reads thinner every time you wait. Stir the bucket fully before each reading, spin the spindle on release to shed drag and bubbles, and let it sit ten seconds before you read the meniscus.

Handled that way, repeat readings on one bucket land within about 0.02 of each other. Wider spreads mean your stirring, not the tool, is inconsistent.

Calibrate against the 100 ml weighing method once a month to confirm both tools agree.

Is Sieving Wet Glaze Safer Than Mixing Dry Powders?

Wet sieving is dramatically safer than dry handling, because material locked in liquid cannot become airborne dust, the delivery route silica uses to reach deep lung tissue. The 2016 OSHA respirable silica limit, 50 micrograms per cubic meter over an eight hour shift, exists precisely because dry powder clouds exceed it by orders of magnitude.

Dry steps still appear, such as weighing batch materials from bags. Keep those brief, slow, and hooded or outdoors, with P100 rated protection.

Convert any dry step you can to wet, and reserve the respirator for the steps that stay dry.

Are Glazed Test Tiles Safe to Use as Small Dishes?

Treat test tiles as wall tools, not tableware, because a test surface exists to answer questions, not to meet food safety standards. Crazed or under tested glaze can trap bacteria in hairline gaps, and no home dish routine reaches them. Anything headed for actual kitchen duty deserves its own verification, and using glazed ceramic cookware safely at home starts from that same screening principle.

An AP seal on a jar describes classroom handling safety, not long term food contact behavior. Food service is a separate test category from tile testing.

Keep tiles on the wall, and glaze a dedicated functional piece for any food use experiment.

Nylon Versus Stainless Steel Mesh: Which Lasts Longer?

Stainless steel mesh outlasts nylon under regular studio use, often for years, while nylon stretches and wears through in months of weekly sieving. Cost splits the difference at about $10 to $15 for nylon against $18 to $40 for 304 or 316 stainless, so the material choice follows your mixing frequency.

Nylon has one honest advantage: it never dents or rusts, and cheap replacement suits a casual schedule. Under a rib and a heavy slurry, stainless keeps its openings true to spec.

Mix weekly and buy stainless once; glaze monthly and nylon does the job.

When Does Dry Sieving Make Sense Instead of Wet?

Dry sieving makes sense before water enters the process at all, for caked material bags, hard lumps in feldspar or whiting, and dry blend preparation for casting slip. Run it outdoors with a P100 respirator at a coarser 40 to 60 mesh, because fine dry powder blinds mesh almost instantly.

The dust cloud around dry sieving is the single highest silica exposure in a home studio. That is why every later step defaults to wet.

Break lumps dry when a bag demands it, then go wet for every step after.

Do You Need a Graduated Cylinder, or Will Any Marked Cup Work?

Any straight walled, one line container works if the 100 ml mark is honest, and you can prove honesty in a minute by filling to the line with water and reading the scale. If the scale shows 100 grams, the vessel is true for plastic cups or kitchen measures alike.

Tapered buckets fail the check, because their marks measure distance up the slope, not actual volume. A graduated cylinder from about $6 to $12 removes all doubt and survives a rinse bucket.

Verify every new container once, then trust to scale, not to the printing.

How Many Test Tiles Should You Make for One New Recipe?

Make at least six tiles per new recipe: two at a standard dip, two for the double dip thickness ladder, and two spares for refires or layered tests. At roughly 25 grams of clay per tile, six tiles cost pennies and save a full kiln load of guessing.

Spares earn their clay whenever a firing lands borderline and needs a repeat. Layered tests consume tiles fast, so stamp eight for anything you suspect you will love.

Plan for six, and stamp two more than you think you need.

How Long Should You Stir a Settled Five Gallon Bucket Before Sieving?

Plan on two to three minutes with a drill mixer, moving the paddle up and down through the bottom layer so the settled material re-enters suspension. Moderate speed wins on consistency: high speed whips in air bubbles that carry dry streaks straight through the mesh.

Watch the bucket wall for your finish line. No visible streaks and no resistance at the paddle mean the bottom let go.

Mix to that signal, then sieve immediately while the solids stay lifted.

How Should You Store a Mixed Test Batch Between Firing Days?

Seal the batch airtight, label it with the recipe code, the date mixed, and the measured specific gravity, and keep it above freezing. Before the next session, remix fully and take a fresh reading, because settling and evaporation drift even sealed jars over months.

Re-sieve anything that formed a skin or a hard layer before the label stays valid. Wide mouth jars with lids suit 100 to 300 ml test batches.

Write the SG on painter’s tape at the lid, so no batch in your studio is ever anonymous.

Where to Begin With Your Next Batch

Glaze testing pays for itself inside one firing: matching bisqued tiles prove fit on your real clay body, an 80 to 100 mesh wet pass kills specks at the source, and a specific gravity log near 1.45 to 1.55 makes every dip repeatable. Start with one 100 gram batch, six stamped tiles, and a scale reading written down before the first dip.

Every tile in the box makes the next recipe question cheaper to answer and every logged number compounds.