What this is
(section missing in design.md)
The design
This instrument is governed by coupled plate/shell vibration plus Helmholtz body resonance.
```text tone_field_f1 ~= (kappa / (2*pi)) * (h / a^2) * sqrt(E / (rho * (1 - nu^2))) ```
Where `h` is local tone-field thickness, `a` is effective field radius, `E` is Young's modulus, `rho` is density, `nu` is Poisson ratio, and `kappa` is an empirical boundary/shape coefficient. For ceramic this equation is a sanity check, not a final predictor.
```text f_gu = c/(2*pi) * sqrt(A_gu / (V_shell * L_eff_gu)) L_eff_gu = wall + 0.6 * sqrt(A_gu/pi) ```
The gu/port resonance should be measured as a coupled body mode. It may support warmth and sustain, but it will not tune the tone fields the way hammered steel tuning does.
The build
Ceramic Hang Assembly Manual
Scope
This manual covers the first ceramic handpan-inspired tonal vessel prototypes. It assumes the instrument is slip-cast from upper and lower shell molds and validated as a research build before decorative finishing.
Tools And Setup
- CAD model for upper shell, lower shell, tone-field islands, gu, rim, and mold split.
- Large-format 3D printer or outsourced print service.
- Plaster mold-making setup: cottle boards, scale, bucket, plaster, mold release, clamps.
- Cone 6 casting slip and known firing schedule.
- Drying cradle and firing support ring.
- Calipers, scale, tuner, microphone, recording app, and spreadsheet/validation log.
- Diamond files/burrs for minimal cleanup.
- Kiln access.
Process
1. **Make shrinkage bars** - Cast or form test bars from the actual clay body. - Fire through the intended bisque and glaze schedule. - Replace the assumed 12 percent shrinkage with measured data before final master printing.
2. **Build tone coupons** - Make small raised/thinned field coupons before a full shell. - Vary thickness, field diameter, relief depth, and clay body. - Record pitch, decay, cracking, and perceived strike feel.
3. **Model the first shell** - Model the fired target geometry first. - Apply `master_scale_factor = 1/(1 - shrinkage)`. - Keep the first upper shell conservative: fewer undercuts, larger radii, and enough wall thickness to survive handling.
4. **Print and seal masters** - Print upper and lower shell masters or segments. - Fill segment seams, sand, and seal. - Mark centerline, tone-field index, rim datum, and gu center.
5. **Make plaster molds** - Build cottle boxes with enough plaster thickness for a large dome. - Include registration and mold handling features. - Dry molds fully before slip casting.
6. **Slip cast shells** - Cast upper and lower shells separately. - Record slip batch, pour time, drain time, demold time, room condition, and measured wall thickness. - Support shells in a cradle as they stiffen.
7. **Join and refine** - Join upper/lower shells at leather-hard stage. - Smooth seam and rim. - Keep post-join tone-field carving minimal and documented.
8. **Dry slowly** - Dry under plastic with frequent inspection. - Watch tone-field edges, gu, rim seam, and support contact points.
9. **Bisque fire and measure** - Fire to the clay body's recommended bisque schedule. - Measure every tone field and the gu/body resonance before glazing. - Decide whether to continue, revise the mold, or return to coupons.
10. **Finish test** - Test glaze or oxide on coupons before the full body. - If glazing the full shell, leave tone-field strike zones and acoustic edges as controlled test variables.
11. **Final validation** - Record pitch, cents error, decay time, body mode, gu response, crack status, and playability. - Feed results back into the next design table revision.
Shop Notes
- Do not chase final tuning on the first shell. The first shell is a measurement object.
- Never grind aggressively on fired tone fields.
- Add a protective rim strategy early; ceramic rims are vulnerable.
- Treat transport as a design requirement, not an afterthought.
No process photos in images/. Add at least one to populate this section.
The numbers
BOM
| item_id | category | item | qty | spec | make_buy | estimated_cost | source_note | drawing_ref | notes |
|---|---|---|---|---|---|---|---|---|---|
| CHG-BOM-001 | Clay | Cone 6 casting slip | 5 gal | Stoneware or porcelain casting slip with measured shrinkage | Buy | derived estimate $40-80 | Date-check before purchase | CHG-DRW-001 | Choose one clay body for the first controlled run. |
| CHG-BOM-002 | Mold | #1 pottery plaster | 75 lb | Absorbent pottery plaster for upper/lower shell molds | Buy | derived estimate $50-90 | Date-check before purchase | CHG-DRW-002 | Large dome molds will consume more plaster than udu/ocarina molds. |
| CHG-BOM-003 | Master | 3D printed upper shell master | 1 | Oversized by measured shrinkage with tone-field islands | Make | derived estimate $40-200 | Print or outsource | CHG-DRW-003 | Segmented print acceptable if seams are filled and sealed. |
| CHG-BOM-004 | Master | 3D printed lower shell master | 1 | Oversized by measured shrinkage with gu port reference | Make | derived estimate $25-150 | Print or outsource | CHG-DRW-004 | Lower shell can be simpler than upper shell. |
| CHG-BOM-005 | Fixture | Drying support cradle | 1 | Breathable foam or plaster cradle | Make | derived estimate $10-40 | Shop-made | CHG-DRW-005 | Prevents dome sagging and rim distortion. |
| CHG-BOM-006 | Fixture | Firing setter or support ring | 1 | Kiln-safe support for shell | Make/Buy | derived estimate $20-120 | Date-check refractory options | CHG-DRW-006 | Must not fuse to body or block shrinkage. |
| CHG-BOM-007 | Tools | Diamond files and burrs | 1 set | Fine diamond abrasive tools | Buy | derived estimate $15-40 | Date-check before purchase | CHG-VAL-001 | For cautious post-bisque edge cleanup only. |
| CHG-BOM-008 | Measurement | Tuner and microphone | 1 | Cent-accurate tuner plus recording mic | Buy | derived estimate $0-150 | Existing tools okay | CHG-VAL-002 | Use same setup across prototypes. |
| CHG-BOM-009 | Measurement | Scale and calipers | 1 set | Mass and dimensional tracking | Buy | derived estimate $0-80 | Existing tools okay | CHG-VAL-003 | Mass change helps track glaze/water loss. |
| CHG-BOM-010 | Finish | Exterior glaze or oxide wash | 1 batch | Cone-compatible finish | Buy | derived estimate $15-60 | Date-check before purchase | CHG-DRW-007 | Test glaze damping on coupons before full shell. |
| CHG-BOM-011 | Protection | Rim wrap or bumper | 1 | Leather/rope/silicone rim protection | Buy/Make | derived estimate $10-75 | Date-check before purchase | CHG-DRW-008 | Protects fragile rim and improves handling. |
| CHG-BOM-012 | Transport | Padded bag/case | 1 | 18-20 in protective case | Buy | derived estimate $40-160 | Date-check before purchase | CHG-DRW-009 | Ceramic transport risk is high. |
Cut list
| item_id | part | qty | rough_dimensions_in | final_dimensions_in | material | operation | fixture_or_tool | yield_note | notes |
|---|---|---|---|---|---|---|---|---|---|
| CHG-CUT-001 | Upper master print segments | 1 set | 20 x 20 x 5 envelope | 18 in fired-equivalent dome scaled for shrinkage | PLA or resin | 3D print and seal | Printer or print service | Segment if printer is smaller than master | Do not treat printed geometry as final until shrinkage bars are measured. |
| CHG-CUT-002 | Lower master print segments | 1 set | 20 x 20 x 3 envelope | 18 in fired-equivalent lower shell scaled for shrinkage | PLA or resin | 3D print and seal | Printer or print service | Segment if needed | Include gu reference and rim registration. |
| CHG-CUT-003 | Upper plaster mold | 1 | 24 x 24 x 8 cottle | Upper dome mold with registration | #1 pottery plaster | Mold pour | Cottle boards | Single-use setup until mold design proven | Plan parting line before printing final master. |
| CHG-CUT-004 | Lower plaster mold | 1 | 24 x 24 x 6 cottle | Lower shell mold with gu area | #1 pottery plaster | Mold pour | Cottle boards | Single-use setup until mold design proven | Keep lower mold simpler for first run. |
| CHG-CUT-005 | Drying cradle | 1 | 20 x 20 x 5 | Support upper shell without point loads | Foam/plaster/soft support | Cut/form | Knife/saw/rasp | Reusable | Must not trap moisture at rim. |
| CHG-CUT-006 | Firing support ring | 1 | 18-20 OD | Support shell rim or neutral zone | Refractory clay/fiber/kiln furniture | Form/cut | Kiln-safe tools | Reusable if it survives | Test with scrap before full shell. |
| CHG-CUT-007 | Tone coupons | 12 | 4 x 4 x variable thickness | 3-4 in test fields | Casting slip or slab clay | Cast/press small coupons | Simple plaster tiles | Many small tests beat one large failed shell | Label every coupon with clay/body/thickness. |
Tuning & validation
| build_id | stage | date | clay_body | shrinkage_expected_pct | master_scale_factor | field_id | target_note | target_freq_hz | field_major_in | field_minor_in | field_thickness_in | measured_freq_hz | cents_error | decay_sec | crack_status | body_mode_hz | gu_hz | action | result | notes |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| CHG-P0 | bisque | TBD | 12 | 1.136 | coupon_A | G4 | 392 | TBD | TBD | TBD | none | Measure coupon before committing full dome | ||||||||
| CHG-P0 | bisque | TBD | 12 | 1.136 | coupon_B | C5 | 523.25 | TBD | TBD | TBD | none | Compare thickness sweep | ||||||||
| CHG-P1 | greenware | TBD | 12 | 1.136 | T1 | Bb3 | 233.08 | 3.4 | TBD | TBD | none | Check drying distortion | ||||||||
| CHG-P1 | bisque | TBD | 12 | 1.136 | T1 | Bb3 | 233.08 | 3.4 | TBD | TBD | TBD | First shell tone-field measurement | ||||||||
| CHG-P2 | bisque | TBD | 12 | 1.136 | Ding | G3 | 196 | 4.0 | TBD | TBD | TBD | TBD | TBD | Measure center ding and gu coupling | ||||||
| CHG-P2 | bisque | TBD | 12 | 1.136 | Gu | TBD | TBD | TBD | TBD | TBD | TBD | TBD | TBD | Tap/blow gu and record body mode | ||||||
| CHG-P3 | glaze_fire | TBD | 12 | 1.136 | TBD | TBD | TBD | TBD | TBD | TBD | TBD | TBD | TBD | Compare glaze shift and damping | ||||||
Known risks
Ceramic Hang Risks
| Risk ID | Category | Risk | Verification Test | Mitigation | | --- | --- | --- | --- | --- | | CHG-RISK-001 | Acoustic | Ceramic tone fields may not sustain like steel handpan fields. | Fire tone coupons and record decay time for at least 12 field geometries. | Pivot to fewer larger fields, a tongue/relief hybrid, or ceramic resonator with metal tone fields. | | CHG-RISK-002 | Acoustic | First-order plate formulas may miss fired pitch by large margins. | Compare predicted vs measured frequency on coupons and first mini dome. | Build empirical correction table before full 9-note shell. | | CHG-RISK-003 | Structural | Raised/thinned tone fields may crack during drying or firing. | Inspect coupon and P1/P2 fields at greenware, bone dry, bisque, and glaze stages. | Increase radii, reduce relief depth, slow drying, change clay body. | | CHG-RISK-004 | Structural | Large slip-cast dome may slump or warp. | Fire a blank dome on proposed setter before tone-field body. | Add support ring, revise dome height, change firing schedule. | | CHG-RISK-005 | Ergonomic | Ceramic body may be too heavy or fragile for lap playing. | Weigh P2 shell and test seated/stand support with non-playing handling. | Use stand/cradle, reduce wall thickness, design protected rim. | | CHG-RISK-006 | Finish | Glaze may damp tone fields or change pitch. | Glaze matched coupons and compare before/after decay/pitch. | Use exterior-only, oxide wash, burnish, or unglazed tone zones. | | CHG-RISK-007 | Supply | Clay body shrinkage may differ from assumption. | Fire shrinkage bars before printing final master. | Update design table and master scale factor. | | CHG-RISK-008 | Fit/Finish | Post-fire grinding may chip tone fields. | Test diamond tool cleanup on scrap fired coupons. | Tune in greenware/bisque stage; avoid aggressive fired correction. | | CHG-RISK-009 | Transport | Finished ceramic shell may break in normal handling. | Drop/handling tests only on failed/scrap shells; case fit check. | Design rim bumper and hard/padded transport case. |