Glaze Mixing Program
From Asmbly Wiki
Purpose
Our glaze program exists to give members safe, reliable, and affordable finishing options while protecting the makerspace from unnecessary risk. Instead of relying on retail, brush-on products with variable ingredient transparency and high per-ounce costs, we formulate and mix studio dip glazes in controlled batches. This approach supports our community mission in five ways:
- Cost stewardship (do more with our budget). Raw glaze materials (clays, fluxes, colorants) purchased in bulk reduce the per-gallon cost of glaze to a fraction of comparable commercial products. Lower unit costs mean we can keep member fees reasonable, keep buckets filled, and allocate more of the ceramics budget to essentials (kiln maintenance, shelves, furniture, tools).
- Ingredient transparency & food-contact accountability. By owning the recipe, we know exactly which oxides are present and at what levels. That lets us:
- avoid or tightly control restricted/toxicants in food-contact glazes,
- label glazes clearly for intended use (e.g., “liner,” “decorative only”) with certainty.
- Consistency and quality control. In-house batching allows us to standardize mixing steps (weighing, sieving, deflocculation/flocculation), target specific gravity/viscosity, and test each batch on reference tiles before release. Members get predictable results across firings because the glaze in the bucket is the same each time.
- Risk management and liability reduction. Centralized control over formulas, labeling, and process minimizes hazards that arise when unknown or altered commercial products are brought into a shared studio. Documented recipes, batch logs, and test tiles provide traceability if an issue arises (e.g., kiln damage, unexpected surface defects, or food-safety concerns).
- Education and community benefit. Our program teaches best practices—safe material handling, glaze chemistry basics, and process discipline—while providing a dependable, shared resource. Members learn why variables like thickness, clay body, and firing schedule matter, and they can make informed, creative choices within safe parameters.
In short, mixing our own glazes gives Asmbly control over costs, safety, and consistency, ensuring members have access to dependable finishes without compromising health, equipment, or budgets.
Method
Our glaze program uses a phased, demand-driven approach managed by trained stewards. This ensures safety, consistency, and sustainable use of volunteer time and budget.
1) Start with a vetted “core set” of glazes
- What we do: The ceramics lead and glaze stewards select an initial batch of widely useful, studio-safe dip glazes that fit our clay bodies and firing schedule.
- Why we do it: Beginning with a proven set limits variables during launch. It lets us refine mixing, labeling, testing, and firing workflows before expanding options—reducing waste, surprises, and kiln risk.
2) Expand recipes based on member demand and safety
- What we do: Additional glazes may be added when there is clear member demand and the recipe is safe to produce (no restricted materials for food-contact, stable at our cone, compatible with our kilns and shelves). Requests are gathered via the ceramics volunteers Slack channel and at steward on duty sessions. Candidate recipes are small-batch tested before adoption.
- Why we do it: New glazes consume chemicals, studio space, kiln space and firing time, as well as volunteer labor. Requiring broad interest and a safety review keeps the lineup useful, affordable, and low-risk for a shared studio.
3) Experienced stewards mix batches at launch
- What we do: Only the glaze stewards designated for the program perform mixing initially. They handle weighing, wetting-out, sieving, setting specific gravity/viscosity, and producing labeled test tiles for approval before a bucket is released to members.
- Why we do it: Mixing involves chemical handling, equipment care, and quality control. Centralizing early batches with experienced stewards builds consistent procedures and a reliable baseline.
4) Train additional stewards through a structured shadow-to-sign-off path
- What we do: Volunteers interested in learning glaze mixing monitor the ceramics volunteers Slack channel for posted opportunities to assist. Training follows a progression:
- Observe a full batch (PPE, dust control, weighing, sieving, cleanup).
- Assist under supervision (measure, sieve, record batch data).
- Lead a batch with a mentor present.
- Sign-off to mix approved recipes independently.
- Why we do it: A clear ladder preserves safety and quality while growing program capacity. It also documents who is competent to handle chemicals and make decisions during mixing.
5) Use a repeatable mixing & QA workflow
- What we do (each batch):
- Pre-check: Confirm approved recipe and inventory of materials.
- Weigh & mix: Measure by mass on calibrated scales; wet-blend to minimize airborne dust.
- Sieve: Pass to the specified mesh to remove agglomerates and improve application.
- Adjust: Set specific gravity/viscosity to target; record numbers on the batch log.
- Test tiles: Apply to standard clay bodies at standard thicknesses; fire on the studio schedule.
- Review & release: When test results match reference (surface, fit, food-contact designation), label the bucket (cone, use, batch ID, SG/viscosity, date) and place it in service.
- Why we do it: Consistency depends on accurate measurement, particle size control, and repeatable rheology. Test tiles and logs create traceability and help diagnose issues quickly.
6) Manage inventory and scheduling
- What we do: Stewards maintain an inventory sheet with target par levels for each glaze. When a bucket reaches the reorder line, a mixing session is scheduled and posted in Slack (inviting trainees if appropriate).
- Why we do it: Proactive scheduling prevents stockouts, aligns volunteer availability with studio needs, and creates predictable learning opportunities.
7) Document everything
- What we do: Keep a batch log (recipe version, mixer, dates, SG/viscosity, sieving notes, test-tile photos, kiln program used, and any anomalies). Changes to a recipe or process are recorded as a new version and announced in Slack.
- Why we do it: Documentation underpins safety, quality, and liability control. If a defect or kiln incident occurs, we can trace causes and fix them without guesswork.
In short: experienced stewards launch and stabilize the core glazes; new glazes are added only when safe and broadly useful; volunteers grow into mixing roles through supervised practice and documented sign-off; and every batch follows the same measured, test-verified workflow for consistent, studio-safe results.
Safety
Glaze mixing is the highest-risk activity in ceramics because it concentrates three hazards at once:
- Respirable dust from finely milled powders (silica, alumina, feldspathic materials) that can lodge deep in the lungs.
- Toxic metal oxides and carbonates (e.g., copper, cobalt, manganese, barium, chrome in some recipes) that pose inhalation and ingestion risks.
- Process intensity (pouring, weighing, sieving) that easily disperses powders into the air and onto surfaces.
Our safety rules are designed to control those risks at the source, protect people nearby, and prevent contamination of the studio.
Who may mix
Only approved glaze stewards may handle dry glaze materials or mix batches.
Why: Trained stewards follow established controls (correct PPE, wet-mixing technique, batch logs) that minimize airborne dust and exposure for everyone in the makerspace.
Where mixing happens
All dry-material handling and mixing occur outdoors in a designated area posted in Slack before each session.
Why: Outdoor air dilution greatly reduces airborne concentration of fine particulates. It also keeps any incidental dust out of the studio and kilns, where it could contaminate surfaces and ware.
Set-up requirements
- Work upwind of bystanders; post cones/tape a 10–15 ft buffer around the mixing table.
- Use a stable, wipeable surface (plastic-covered table or dedicated cart).
- Keep water on hand for wet-methods and immediate cleanup.
Required PPE
For mixers and helpers (mandatory):
- Respiratory protection: NIOSH-approved P100 (elastomeric half-face with P100 cartridges or P100 disposable) for any dry-material handling.
- Perform a user seal check each time. Facial hair that breaks the seal is not compatible with a tight-fitting respirator.
- Gloves: Nitrile or equivalent, changed when soiled.
- Eye protection: Safety glasses; use a face shield during vigorous sieving or when splashing is likely.
- Footwear: Closed-toe, non-mesh shoes.
Clothing / outer layer (strongly encouraged, see heat note):
- Long sleeves or a shed-able outer layer (lab coat, work shirt, Tyvek). Why: Sleeves reduce skin contamination and make it easy to remove dust before re-entering the building. In Texas heat, the outer layer is optional for comfort, but it remains the best practice.
Handling practices (how we keep dust down)
- Add powder to water—never water to powder. Why: Wetting particles as they enter the bucket minimizes airborne dust.
- Pour low and slow; scoop instead of dumping. Why: Short drop distances and controlled flow prevent plumes.
- Keep lids closed on bags and buckets when not in active use. Why: Limits incidental dispersal by wind.
- Sieve wet, not dry. Why: Wet sieving removes agglomerates without aerosolizing particles.
- Measure by mass on calibrated scales. Why: Accuracy prevents rework and extra handling time (less exposure overall).
- No food, drink, or touching your face during mixing. Why: Prevents ingestion pathways.
Cleanup (what’s allowed and what isn’t)
- Wet wipe surfaces and tools; do not dry sweep or use compressed air. Why: Wet methods trap dust; sweeping and air hoses re-suspend it.
- Collect slurry rinse water in a settling bucket; follow the studio’s waste protocol for decanting and disposing of settled solids. Never pour concentrated slurry down drains. Why: Protects plumbing, traps heavy solids, and keeps metals out of wastewater.
- Place soiled wipes and disposable sheeting in a sealed trash bag.
Re-entry to the studio (clothing & decontamination)
- Brush-off is not enough. If you did not wear a shed-able outer layer, do not linger in the studio after mixing. Why: Dust on clothing migrates to shared benches, wheels, and ware.
- If your outer layer shows visible dust, bag it outside and launder it separately; do not bring it into the building. Why: Prevents cross-contamination of the indoor environment.
- Handwashing with soap and water is required before touching studio equipment.
Prohibited practices
- Mixing or handling dry materials indoors.
- Dry sweeping, compressed air, or leaf blowers for cleanup.
- Open-toed shoes or mesh footwear.
- Allowing untrained members, children, or pets inside the buffer zone.
- Bringing unvetted, unlabeled powders for studio use.
Why: Each of the above either increases exposure risk, contaminates the studio, or undermines traceability.
Health monitoring & incident response
- If you experience coughing, throat irritation, dizziness, or eye irritation during mixing, step away upwind immediately and inform the steward lead.
- For splashes to eyes/skin, flush with water for 15 minutes and report the incident.
- Report any spill, PPE failure, or near-miss so we can improve procedures.
Why this matters for everyone—mixers and non-mixers alike
Controlling dust at the source protects:
- People: reduces risk of respiratory disease and metal exposures.
- Equipment: keeps kilns, shelves, and wheels free of contaminant films that can damage ware and elements.
- Community trust: members can work confidently knowing glaze mixing is tightly managed.
Bottom line: Glaze mixing is restricted, conducted outdoors, and done under strict PPE and cleanup protocols because that’s what it takes to keep a shared studio safe, clean, and healthy.
