Quick Answer

A quartz tank is a fabricated fused silica vessel used where process media—hot acid, alkaline etch, plating solution, high-purity reagent—demands thermal stability, chemical inertness and low extractables that metal and fluoropolymer cannot both deliver. FGQuartz builds quartz tanks to customer drawing: rectangular or cylindrical body, welded flange rim, bottom drain or side port, optional heating jacket, sight window and agitator port, then fire-polished on all wetted edges. Wall distribution, flange transition and stress relief are reviewed before cutting begins, because a tank lives or fails at the corner radii and the flange root, not at the flat wall.

Key Takeaways

  • Quartz tanks replace PTFE, PFA and PP where temperature exceeds fluoropolymer limits or where extractables must be minimal.
  • Tank body is flame-worked or CNC-joined from plate and tube stock; flange rim, drain port, side ports and jacket are flame-welded, not mechanically assembled.
  • Wall thickness, corner radius and flange-root transition decide cycle life—drawing dimensions alone are not enough.
  • Heating jacket, sight window, agitator port and drain valve interface are designed in during the tank, not added after.
  • Devitrification, flange-root cracking and thermal shock are the three failure modes worth designing against.

Anatomy of a Quartz Tank

A fabricated quartz tank is not a single molded shell—it is a welded assembly of plate, tube sections and flanged rims. Understanding the parts helps specify them.
Body​ — Rectangular (most wet bench and etching lines) or cylindrical (reaction, storage). Rectangular tanks are flame-welded from plate stock: four sidewalls plus bottom, corner-to-corner. Cylindrical tanks start from a tube section with welded end and flange.
Flange rim​ — The load-bearing edge that sits on the bench frame or jacket shoulder. Flatness of the flange face decides sealing behavior. Flange is flame-welded to the sidewall, then fire-polished.
Bottom​ — Plate welded to sidewalls. Drain port is either a flame-drawn nozzle in the bottom corner or a side port near the base. Bottom corner radius is the first place stress concentrates in a loaded tank.
Drain and side ports​ — Flame-drawn nozzles, sometimes with fused silica-to-metal transition for valve interface. Diameter, position and number are set by bench plumbing.
Heating jacket (optional)​ — A secondary fused silica envelope around the tank body, with fluid inlet and outlet. Used when the process media must be held above ambient. Jacket wall, inlet position and flow path are co-designed with the tank body so hot spots do not land on a corner.
Sight window (optional)​ — Fire-polished fused silica disc or view port welded into a sidewall or the lid, positioned for operator view of liquid level or bubble behavior.
Lid and cover (optional)​ — Plate with lift handle, sometimes with passthroughs for probe, dip tube or agitator shaft.
Agitator port (optional)​ — Reinforced opening in lid or sidewall for magnetic stirrer coupling or dip tube, with fused silica-to-metal transition if the agitator assembly is metal.

Quartz Tank vs Alternatives — When Quartz Wins

Candidate
Temperature ceiling
Ion extractables
Chemical resistance
Where it loses
PP and PVC
Low
Moderate
Adequate for dilute cold acid
Temperature, long-term creep
PTFE and PFA
Moderate
Very low
Excellent for most acids
Temperature still bounded, mechanical stiffness low, cost
Stainless and Hastelloy
High
Metallic ions
Dependent on alloy vs media
Ion contamination in high-purity reagent
Fused silica quartz
High, with thermal shock limits
Minimal
Excellent for acids, except HF and hot concentrated alkali
Impact fragility, thermal shock if filled cold-to-hot
Quartz wins when the process needs high temperature, low extractables and acid stability​ simultaneously. It loses to PTFE on impact resistance and to metal on mechanical robustness, but those belong to different benches.
Note: hydrofluoric acid and hot concentrated alkali attack fused silica. Short-dwell dilute HF in semiconductor wet processes is a separate discussion with grade and dwell limits; hot concentrated caustic shifts the material conversation away from quartz entirely.

Application Analysis

Wet Bench and Acid Etching

Rectangular quartz tanks on automated etch lines: sulfuric-peroxide mixtures, phosphoric acid, sulfuric-peroxide hydrogen peroxide mixes. Tank sees hot acid, periodic dump, rinse, refill. Flange rim sits on the bench frame; drain port at rear corner; sight window on the operator side; optional jacket under the tank for pre-heat. Wall thickness is set by acid temperature and dump frequency, not by a generic rule.

Plating and Electrolytic Lines

Quartz tanks for plating baths where metallic ion contamination from steel or plastic stabilizer must be avoided. Sometimes heated, sometimes with agitator port. Quartz does not conduct, so tank wall itself is not part of the circuit—this is why quartz is chosen over steel for high-purity plating.

High-Purity Reagent and Pharmaceutical Water Loop

Storage and dispense tanks for reagents where even trace extractables shift yield. Fused silica grade selected by transmission and hydroxyl class; all wetted seams fire-polished; drain port positioned to avoid dead leg. Tank is often rectangular with tight flange flatness so the bench lid seals clean.

Laboratory and Pilot Reaction

Smaller quartz tanks as reaction vessels—sometimes cylindrical with jacket, sometimes rectangular with multiple side ports for feed, vent, thermowell. Agitator port in lid with fused silica-to-metal transition. Volume ranges from bench-top to pilot, but the design logic is the same: wall, corner radius, flange root, jacket inlet position.

Semiconductor Wet Process

Quartz tanks in wafer wet stations for cleaned chemistry, dilute HF short dwell, IPA dry and similar steps. Here the tank competes with PFA; quartz is chosen when temperature exceeds PFA comfort or when the bench designer wants a stiffer wall and better visual through the sight window. Flange flatness and drain corner radius are the two design items that decide whether the tank survives install or cracks on the first thermal cycle.

Grade Selection

Quartz tanks are specified by fused silica grade and transmission class, matched to the process media and temperature:
  • Deep-UV grade​ — high-purity reagent and semiconductor wet where transmission and hydroxyl matter
  • UV-visible grade​ — standard acid etching, plating, general wet bench
  • Infrared-biased grade​ — industrial acid and alkaline where transmission spec is relaxed, temperature stability is the priority
Process cleanliness, pre-bake and handling carry as much weight as grade. A high-grade tank mishandled will shed sooner than a mid-grade tank under a clean protocol.

Common Problems

Devitrification on wetted surfaces​ — Milky crystalline patches on the inner wall. Triggered by media chemistry, temperature, grade and cleaning protocol. Not a machining defect. Tank grade, media formulation and post-run cleaning are the levers.
Flange-root cracking​ — The transition from vertical sidewall to horizontal flange rim is where thermal gradient and bench load concentrate. If the transition radius is too tight or the flange flatness is uneven on the frame, the root cracks after cycles.
Bottom corner stress​ — The weld between sidewall and bottom plate, plus the drain nozzle if present. Corner radius, wall distribution and drain position decide whether the tank dumps clean or cracks at the corner after a thermal swing.
Thermal shock on fill​ — Filling a room-temperature tank with hot acid, or vice versa, can initiate surface cracks if the wall distribution and fill rate are not considered. Jacketed tanks mitigate this by pre-warming the envelope.
Sight window fogging or devitrification​ — Sight windows see the same media as the tank wall but with a different curvature and edge condition. Fire-polish quality on the window weld decides longevity.
None of these are bad quartz. They are specification gaps between media, temperature, tank geometry and installation condition.

Selection Guide — How to Spec a Quartz Tank

Step 1 — Media and temperature​ — Acid, alkaline, solvent or reagent? Concentration? Temperature range: ambient, heated or jacketed? This decides grade and whether quartz is the right material at all.
Step 2 — Form factor​ — Rectangular for wet bench and etching lines, cylindrical for reaction and storage. Length, width and height, or diameter and height. Flange rim on top, or rimless with lip?
Step 3 — Ports​ — Drain position and diameter. Side ports: number, position, purpose. Sight window: position and size. Agitator port: lid or sidewall, fused silica-to-metal transition needed?
Step 4 — Jacket​ — Heated or ambient? If heated, fluid type, inlet and outlet position, maximum jacket temperature. Jacket wall thickness and flow path co-designed with tank body.
Step 5 — Flange and sealing​ — Flange face flatness tolerance, seal type, frame interface. This is where the tank meets the bench—flatness and rim relief matter more than wall thickness.
Step 6 — Grade​ — By transmission and hydroxyl need, not by a number. Deep-UV for high-purity reagent and semiconductor wet; UV-visible for standard etching, plating and general wet bench; infrared-biased for industrial acid where temperature stability leads.
Send media, temperature, dimensions, port list and bench interface, or the drawing set. Design review returns a tank proposal with wall distribution, corner radius, flange transition and jacket layout noted—not just a yes.

FAQ

Q: What is a quartz tank used for?
A: Fused silica tanks are used where process media—hot acid, alkaline etch, plating bath, high-purity reagent—require thermal stability, chemical inertness and low extractables that metal and fluoropolymer cannot both deliver. Common on wet benches, etching lines, plating lines, reagent storage and lab reaction.
Q: Quartz tank vs PTFE or PFA tank—which?
A: PTFE and PFA handle most acids at moderate temperature and resist impact better. Quartz handles higher temperature, holds a stiffer wall with better sight-window clarity, and gives lower extractables in some high-purity contexts. If the process exceeds PTFE temperature or needs a rigid wall with vision, quartz. If impact or HF or hot alkali is the concern, PTFE or another material.
Q: Can a quartz tank have a heating jacket?
A: Yes. A secondary fused silica envelope surrounds the tank body with fluid inlet and outlet. Jacket wall, inlet position and flow path are co-designed with the tank so hot spots avoid corners. Used for etch pre-heat, reagent warm-hold and temperature-controlled processes.
Q: Can you put drain ports, sight windows and agitator ports on a quartz tank?
A: Yes. Drain nozzles are flame-drawn at the bottom corner or base side. Sight windows are fire-polished discs welded into a sidewall. Agitator ports go in the lid or sidewall, often with a fused silica-to-metal transition for the agitator assembly. All are flame-welded, not mechanically threaded into quartz.
Q: Why do quartz tanks devitrify?
A: Devitrification is surface crystallization of fused silica, triggered by media chemistry, temperature, grade and cleaning protocol. It is not a machining defect. Tank grade, media and post-run cleaning are the controls.
Q: What grade for a quartz tank?
A: Deep-UV grade for high-purity reagent and semiconductor wet; UV-visible grade for standard etching, plating and general wet bench; infrared-biased grade for industrial acid or alkaline where transmission is relaxed and temperature stability leads. Process cleanliness and handling carry equal weight.
Q: Can you build to drawing with low volume?
A: Yes. Prototype single piece through volume production. Design review is done before quotation so wall, corner radius, flange transition and jacket layout are set before cutting.
Q: Do you ship assembled or flange-only?
A: Tanks ship as welded assemblies: body, flange, ports, and if specified, jacket, sight window and lid. For large frames, flange rim and tank body are shipped together; jacket and plumbing interface are pre-fit if the drawing includes them.
Q: What file formats for RFQ?
A: DXF, STEP, IGES, PDF. For replacement tanks, bench model, media, temperature and dimensions are often enough to start; for new benches, the drawing set triggers design review.
Q: What media should not go in a quartz tank?
A: Hydrofluoric acid and hot concentrated alkali attack fused silica. Short-dwell dilute HF in semiconductor wet is a separate discussion with grade and dwell limits; hot concentrated caustic shifts the material conversation away from quartz entirely.
Q: How to avoid thermal shock when using a quartz tank?
A: Control fill rate, pre-warm the tank when process allows, use flexible connections to avoid piping strain, and review corner radius and wall distribution during design. Jacketed tanks help by pre-warming the envelope before the process media enters.

Conclusion

A quartz tank is not a container—it is a thermal and chemical envelope where media, temperature, wall distribution, flange transition and jacket layout either align or the tank tells you about it after the first thermal swing. FGQuartz flame-welds, CNCs and fire-polishes in-house, so body, flange, ports, jacket and sight window are reviewed as one design pass, not a series of vendor handoffs. Send media, temperature and drawing—get a tank that fits the bench and survives the cycle.