Ocarina Build Packet — Tony Koop's Build Log

What this is

(section missing in design.md)

The design

Ocarinas behave primarily as Helmholtz resonators:

```text f = c/(2*pi) * sqrt(A_open/(V_chamber * L_eff)) ```

Unlike a transverse flute or Native American style flute, pitch is driven by chamber volume and total open-hole area, not tone-hole distance along a bore. Hole position is still important for ergonomics, grip, and fingering logic.

ocarina-body-section

ocarina-hole-layout

ocarina-mold-schematic

The build

Ocarina Assembly Manual

Scope

This manual covers a slip-cast or press-molded ceramic ocarina based on `docs/Ocarina.xlsx`. It is written for prototype builds where the first goal is repeatable tone and validated tuning, not decorative finish.

Tools

CAD package for master design.
3D printer and sanding/sealing supplies.
Cottle boards, plaster mixing bucket, scale, mold soap, and clamps.
Stoneware slip or workable clay body.
Small hole cutters, drill bits, needle tools, loop tools, ribs, sponge, and fettling knife.
Chromatic tuner, microphone, calipers, graduated syringe or water-fill vessel.
Diamond needle files or fine diamond burrs.
Wax resist, glaze, and kiln access.

Process

1. **Set design inputs** - Confirm target ocarina size, chamber volume, voicing window, wall thickness, clay body, and shrinkage. - Create a build ID before CAD begins.

2. **Model the master** - Model the body as a controlled-volume vessel. - Include split-line planning, registration features, and a fipple strategy. - Scale the master by `1/(1 - measured_shrinkage)`.

3. **Print and finish the master** - Print the master with enough wall strength to survive mold making. - Sand layer lines and seal the surface. - Mark datums: centerline, mouthpiece axis, split plane, and hole reference side.

4. **Make the mold** - Apply release to the sealed master and cottle surfaces. - Pour plaster with at least 1.5 inches around the master where practical. - Add registration keys and dry the mold fully before casting.

5. **Cast or press the body** - For slip casting, pour slip, wait for target wall buildup, drain, and demold at leather-hard stage. - For press molding, press even clay slabs into both mold halves and join with scored slip. - Measure sample wall thickness at a noncritical trimmed area.

6. **Cut fipple and holes** - Establish the windway first. - Cut the labium cleanly and test blow before the body fully dries. - Cut finger holes undersized.

7. **Dry slowly** - Dry under plastic until moisture equalizes. - Watch the mouthpiece and seam areas for cracks.

8. **Bisque fire** - Bisque to the clay body's recommended schedule. - Measure mass, volume, hole diameters, and frequencies.

9. **Tune after bisque** - Enlarge holes to raise pitch. - Refine the fipple only in small steps. - Record measured frequency and cents error after each change.

10. **Glaze** - Wax resist the windway, labium, holes, and any interior opening. - Keep glaze away from the acoustic edges.

11. **Final fire and validation** - Fire to the chosen glaze schedule. - Re-measure all tuning points. - Save final dimensions and tuning data back into the validation log.

Failure Modes To Watch

Weak or no tone: windway too tall, labium too blunt, air jet missing edge.
Pitch too flat: chamber too large, open area too small, or neck length too long.
Pitch too sharp: chamber too small, open area too large, or over-filed holes.
Warped mouthpiece: uneven drying or thin unsupported fipple geometry.
Glaze-choked note: glaze reduced hole or windway opening.

The numbers

BOM

item_id	category	item	qty	spec	make_buy	estimated_cost	source_note	drawing_ref	notes
OCA-BOM-001	Master	3D printed body master	1 set	PLA or resin printed top and bottom master	Make	$2-5	Workbook estimate not date-checked	OCA-DRW-001	Scale master for measured clay shrinkage.
OCA-BOM-002	Mold	#1 pottery plaster	10 lb	USG #1 pottery plaster or equivalent	Buy	$15-25	Workbook estimate not date-checked	OCA-DRW-002	Enough for several small mold sets depending on cottle size.
OCA-BOM-003	Clay	Cone 6 stoneware slip or clay body	25 lb	Slip casting body or press-moldable clay	Buy	$20-35	Workbook estimate not date-checked	OCA-DRW-003	Record batch and measured shrinkage.
OCA-BOM-004	Finish	Cone 6 exterior glaze	3-5 pints	Food-safe or durable ceramic glaze	Buy	$30-60	Workbook estimate not date-checked	OCA-DRW-004	Mask fipple, holes, and interior.
OCA-BOM-005	Tuning	Diamond needle files	1 set	Assorted profiles	Buy	$10-20	Workbook estimate not date-checked	OCA-DRW-005	Needed after bisque and final fire.
OCA-BOM-006	Tuning	Chromatic tuner or analysis app	1	Cent-accurate tuner	Buy	$15-30	Workbook estimate not date-checked	OCA-VAL-001	Use same app/settings across prototypes.
OCA-BOM-007	Mold	Mold soap or release	1 bottle	Murphy's oil soap or mold release	Buy	$5-10	Workbook estimate not date-checked	OCA-DRW-002	For sealed master and plaster parting surfaces.
OCA-BOM-008	Firing	Bisque and glaze firing	per load	Cone 06 bisque and Cone 6 glaze	Buy	$20-50/load	Workbook estimate not date-checked	OCA-VAL-002	Record firing schedule and kiln location.
OCA-BOM-009	Masking	Wax resist	1 small jar	Brushable wax resist	Buy	TBD	Add supplier/date before purchase	OCA-DRW-004	Protect tuning-critical holes and fipple.
OCA-BOM-010	Measurement	Graduated syringe or burette	1	Water-fill volume measurement	Buy	TBD	Add supplier/date before purchase	OCA-VAL-003	Needed for chamber volume validation.

Cut list

cut_id	part	qty	rough_dimensions_in	final_dimensions_in	material	orientation	operation	tolerance_in	yield_or_offcut	notes
OCA-CUT-001	Master body upper half (3D-printed)	1	4.50 x 3.50 x 2.50 envelope	master scale = 1/(1-shrinkage); for 12% shrinkage = 1.136x fired body	PLA or sealable resin	X along mouthpiece axis; Z up; mark split-line and chamber datum	Print, sand layer lines, fill voids, seal/sand, sign with build ID	+/-0.010	Save offcut sprues for shrinkage coupons	Master scale factor must be re-derived from MEASURED clay shrinkage before final master.
OCA-CUT-002	Master body lower half (3D-printed)	1	4.50 x 3.50 x 2.50 envelope	mirror of OCA-CUT-001	PLA or sealable resin	X along mouthpiece axis; Z up; mark split-line	Print, sand, fill, seal	+/-0.010	Reuse offcut sprues for shrinkage coupons	Same scale factor as OCA-CUT-001.
OCA-CUT-003	Wooden cottle boards (mold making)	4	8 x 6 x 0.75 each	7.50 x 5.50 x 0.75 each	Melamine-faced MDF or sealed plywood	Smooth face inward; mark inner clamping zone	Cut, edge-seal, drill clamping holes	+/-0.030	One sheet of 24 x 18 x 0.75 yields all 4	Clean parting wax/release before each pour.
OCA-CUT-004	Plaster mother mold half (poured)	2	7.50 x 5.50 x 2.00 each	7.50 x 5.50 x 1.50-1.75 each (around master)	USG #1 pottery plaster (or equiv.)	Pour with master keyed to first half; second half over registration	Mix to 73:100 water:plaster (by weight); 2-min slake; pour around sealed master	+/-0.060	Trim spew/edge after demold; recover small offcuts as test slabs	Min 1.50 in plaster around master where practical for stiffness.
OCA-CUT-005	Greenware vessel (slip-cast)	1 per pour	~3.95 x 3.07 x 2.20 (master cavity wet)	~3.50 x 2.72 x 1.95 fired (12% shrink)	Cone 6 stoneware casting slip	Mouthpiece axis along master split	Slip pour > drain at target wall (~0.16 in / 0.4 cm) > demold leather-hard	N/A (process-controlled)	Reuse demold trim/fettling waste as slip recycle	Wall thickness drives drying time and tap tone — measure on noncritical trim.
OCA-CUT-006	Voicing window cut (leather-hard)	1	N/A	0.354 x 0.197 (window W x H = 0.9 x 0.5 cm per design)	Cone 6 greenware	Cut perpendicular to mouthpiece axis	Score, lift, clean labium edge with rib	+/-0.010	N/A	Cut undersized; tune by enlarging at bisque tuning step.
OCA-CUT-007	Finger holes (12-hole layout — leather-hard)	12	N/A	0.16-0.31 dia each (start undersized; see design table OCA-DRW-005)	Cone 6 greenware	Per fingering chart row D40:F51 of design table	Brass tube cutter or hole punch; clean burr with damp finger	+/-0.010 (start)	N/A	All 12 holes start at design-table 'minimum' diameter; enlarge at tuning.
OCA-CUT-008	Post-bisque tuning trim	as needed	N/A	Within +/-25 cents of target frequency per validation.csv	Bisqued ceramic	N/A	Diamond needle file or fine diamond burr in steps	+/-0.005 dimensional; +/-25 cents acoustic	Diamond burr offcuts are kiln dust — bag and discard	Document each enlarge step on validation row.
OCA-CUT-009	Wax resist mask (pre-glaze)	1 application	N/A	~0.020 in dry film over voicing window + all 12 holes + interior	Brushable wax resist	N/A	Brush-apply; dry per supplier; check all openings clear	Visual	N/A	Mask all acoustic edges to keep glaze out of windway and holes.
OCA-CUT-010	Glaze application (exterior only)	1 application	N/A	~0.005-0.010 in per coat; 1-2 coats exterior	Cone 6 satin or matte glaze	Avoid waxed regions	Dip / brush / spray exterior only	+/-0.005 (visual)	N/A	Glaze in voicing window or holes will detune the instrument.

Tuning & validation

build_id	stage	chamber_volume_cm3	wall_thickness_cm	voicing_w_cm	voicing_h_cm	hole_id	target_note	target_freq_hz	notes
OCA-P0	voicing_tile					all_closed	A4	440	Practice fipple before full body.
OCA-P1	greenware	130	0.4	0.9	0.5	all_closed	A4	440	Measure before drying if possible.
OCA-P1	bisque	TBD	TBD	TBD	TBD	all_closed	A4	440	First real model check.
OCA-P1	glaze_fire	TBD	TBD	TBD	TBD	all_closed	A4	440	Record glaze shift.
OCA-P2	bisque	TBD	TBD	TBD	TBD	hole_1	Bb4	466.2	Start undersized and enlarge gradually.
OCA-P2	bisque	TBD	TBD	TBD	TBD	hole_2	B4	493.9	Record hole diameter after tuning.
OCA-P2	bisque	TBD	TBD	TBD	TBD	hole_3	C5	523.3	Check breath pressure sensitivity.
OCA-P3	glaze_fire	TBD	TBD	TBD	TBD	hole_12	A5	880	Full 12-hole validation row.

Known risks

Risks

This file was scaffolded by `migrate_packet.py` during the v3 → v4 upgrade. Run `red-team` specialist or fill in by hand.