How to Choose CMC for Ceramic Tile Bodies, Glazes and Printing Glazes
How CMC works as a green-body binder, glaze suspension aid and printing-glaze thickener, with a selection guide to Sentai's nine ceramic grades from DS 0.6 to ≥ 1.0.
Sentai Applications Lab · · 6 min read
For tile bodies, use an economical CMC at a very low addition to raise green and dry strength without upsetting slip deflocculation. For glazes and engobes, use a higher-DS, higher-purity grade that tolerates the soluble salts released by frits and raw materials, keeps the slip suspended and binds the raw glaze to the body. For screen-printing glazes, use a low-viscosity, high-DS grade that builds body without stringiness, so prints stay sharp.
What CMC does in ceramics
CMC is a temporary, organic processing aid. Before firing, it binds particles together, controls the rheology of slips and pastes, and regulates how fast water leaves a glaze layer. It burns out during firing, leaving only a trace of sodium. Its anionic carboxymethyl groups adsorb on clay and glaze particles, so the same molecule can act as binder, suspending agent and, at low levels, part of the deflocculation balance.
Tile bodies: green and dry strength
In floor and wall tile production, the body slip is milled and spray-dried at high solids, then pressed, dried and fired. A small addition of CMC, typically 0.05–0.15 %, raises the green and dry strength of pressed tiles, so fewer pieces break during handling, glazing and kiln loading. Because CMC also raises slip viscosity, the addition must be balanced against the deflocculant, usually sodium silicate or a phosphate, and against the slip solids.
Body binding is a cost-sensitive application where clarity and salt tolerance matter less. Sentai's lower-DS, lower-purity grades, such as C-0664 (DS ≥ 0.6, purity ≥ 60 %) and C-1583 (DS ≥ 0.8, purity ≥ 80 %), are cost-effective choices. Check the effect on dry modulus of rupture and on spray-dryer behaviour when you trial them.
Glazes and engobes: suspension, adhesion and surface quality
In glaze slips, CMC keeps frit and pigment particles suspended so the slip neither settles nor packs hard, controls the drying rate of the applied layer, and binds the raw glaze to the body so it survives handling. A well-bound, evenly drying glaze shows fewer pinholes and crawling defects after firing. Typical additions are 0.1–0.3 %.
Glazes contain soluble salts: frits release alkali and boron ions, and raw materials add others. These ions screen the charge on CMC, reduce its viscosity and, with low-DS grades, can cause haze or gelation. Higher-DS, higher-purity grades such as C-1001 (DS ≥ 1.0) and C-1002 (DS ≥ 0.95), both at purity ≥ 95 %, keep glaze rheology more stable. Choose a higher-viscosity grade such as C-1592 for stronger suspension at a lower addition, or C-0492 when a dense glaze must stay fluid.
Why glaze slips drift
A glaze that loses viscosity over days of storage is usually suffering from one of two problems. Microbes can break down CMC, especially in warm glaze rooms, which shows up as falling viscosity and sometimes an odour; preservatives and fresh batches solve it. Ions leaching from frits can also change the slip over time, and a higher-DS grade reduces that sensitivity. Control the slip daily by specific gravity and flow time, not only by eye.
Printing glazes and decorative inks
Screen-printing and similar decorative glazes need a paste that flows through the screen under shear, recovers quickly to hold a sharp edge, and levels without spreading. A low-viscosity CMC used at a higher concentration gives body with short, non-stringy flow, and a high DS ensures a clean, gel-free solution, because a single undissolved gel can block the screen mesh. Sentai 9L (30–50 mPa·s at 1 %, DS ≥ 0.9) is designed for printing glazes.
Sentai's nine ceramic grades
| Grade | DS | Purity | 1 % viscosity (mPa·s) | Typical starting role |
|---|---|---|---|---|
| C-1001 | ≥ 1.0 | ≥ 95 % | 400–700 | Glazes with high soluble-salt content |
| C-1002 | ≥ 0.95 | ≥ 95 % | 400–700 | General glazes and engobes |
| C-1592 | ≥ 0.9 | ≥ 95 % | 800–1,200 | Glaze suspension at lower addition |
| C-0492 | ≥ 0.95 | ≥ 95 % | 200–400 | Dense glazes that must stay fluid |
| C-1583 | ≥ 0.8 | ≥ 80 % | 800–1,200 | Body binder and engobes |
| C-0664 | ≥ 0.6 | ≥ 60 % | 400–700 | Economical body binder |
| C-2074 | ≥ 0.9 | ≥ 90 % | 2,000–2,500 | High thickening for bodies and glazes |
| 9H | ≥ 0.8 | ≥ 90 % | 2,500–3,500 | Maximum suspension at the lowest addition |
| 9L | ≥ 0.9 | ≥ 90 % | 30–50 | Screen-printing glazes |
Troubleshooting CMC-related defects
| Symptom | Possible CMC-related cause | What to try |
|---|---|---|
| Glaze settles or packs hard | Too little CMC, or CMC degraded in storage | Raise the addition or the viscosity grade; add a preservative |
| Raw glaze cracks on drying | Too much CMC or too fast drying | Reduce CMC or switch to a lower-viscosity grade; adjust drying |
| Crawling after firing | Poor adhesion or high drying shrinkage of the raw glaze | Rebalance CMC and water; check for dust on the body surface |
| Pinholes | Entrained air or undissolved gels | Hydrate fully and deaerate; use a higher-DS grade |
| Blurred prints or blocked screens | Wrong viscosity or gels in the paste | Use a low-viscosity, high-DS grade such as 9L and filter the paste |
| Viscosity drift between batches | Variable soluble salts or water quality | Use a higher-DS grade; control water quality and slip specific gravity |
How Sentai can help
Sentai's ceramic-grade CMC family spans nine standard grades from DS 0.60 to ≥ 1.0 and 1 % viscosity from 30 to 3,500 mPa·s, and a high-end ceramic grade was launched at the 40th China International Ceramics Industry Exhibition in June 2026. Send your body or glaze recipe, application method and current CMC, and the applications team will suggest a starting grade and dose. Free 100–300 g samples are available, and industrial grades ship from a 1 t minimum order.
FAQ
What does CMC do in a ceramic glaze?+
CMC keeps glaze particles suspended, controls the drying rate of the applied layer and binds the raw glaze to the body so it survives handling. The result is a smoother fired surface with fewer pinholes and crawling defects.
How much CMC should be added to a glaze or tile body?+
Typical additions are 0.1–0.3 % for glazes and 0.05–0.15 % for tile bodies. Optimise the dose together with the deflocculant and water content of your own slip.
Why does my glaze slip lose viscosity over time?+
The most common causes are microbial breakdown of the CMC during storage and ions leaching from frits. Add a preservative, keep batches fresh and use a higher-DS grade, which is less sensitive to soluble salts.
Which CMC is best for screen-printing glaze?+
A low-viscosity, high-DS grade that dissolves without gels, so the paste prints sharply and does not block the screen. Sentai 9L, with a 1 % viscosity of 30–50 mPa·s and DS ≥ 0.9, is designed for printing glazes.
Why do ceramic CMC grades range from DS 0.6 to above 1.0?+
Higher DS improves salt tolerance and solution clarity, which matters for glazes containing soluble salts and for printing glazes. Lower-DS, lower-purity grades are cost-effective body binders where those properties are less critical.
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