Quartz is not a commodity metal, so generic RFQ templates copied from steel or aluminium RFQs leave the fabricator guessing on grade, traceability, and inspection scope; the result is a quote that either includes heavy contingency or comes back marked "resubmit with grade callout" [S3][S4]. Engineers who buy advanced material for semiconductor, photovoltaic, or high-temperature structural builds should treat quartz the same way they treat titanium or Inconel: grade on the line, cert on the line, and substitution rules on the line.
Grade, Form, and Stock Condition on the RFQ Line
The stock form line should read "fused silica slab 300 mm x 300 mm x 25 mm, flame-fused, OH less than 10 ppm" or "fused quartz tube OD 50 mm x wall 5 mm x length 1000 mm, electrically fused"; plate, tube, rod, and disk each have different sawing, drilling, and annealing routes, so leaving the form vague pushes the fabricator to add a stock-sourcing line item and a 10-20% contingency on the cut yield [S1][S3]. State also whether customer-furnished stock is acceptable, and whether flame-polished, lapped, or as-cut edges are required on delivery; quartz material stock often ships with a controlled surface that the buyer will either preserve or grind off, and that decision must be on paper before the quote goes out.
Tolerances, Surface Finish, and Optical Clarity
For structural quartz parts, the practical tolerance band is plus/minus 0.1 mm to plus/minus 0.5 mm on cut dimensions and plus/minus 0.05 mm on thickness for lapped plate, with surface roughness 60-80 Ra for as-cut and 4-8 Ra for polished faces; tighter than that and the quote enters the optical-grade price tier, which can multiply unit cost by 3-5x [S1][S2].
Buyers should split the callout into "function-critical" and "reference" tolerances the same way the general fabrication guides do for metalwork, because the fabricator will price critical features with diamond grinding and reference features with standard saw cuts [S1]. For parts that will be bonded, metallised, or heated, also call out the glass quartz surface preparation (fire polish, acid etch, or no prep), because bond strength varies sharply with the as-delivered surface state.
Thermal, Mechanical, and Chemical Operating Envelope
The maximum continuous service temperature for fused quartz is roughly 1050-1100 degC and for fused silica roughly 1100-1200 degC, with a softening point near 1650 degC; the RFQ should state the peak operating temperature, the ramp rate (degC per minute), and the number of thermal cycles, because these parameters drive the annealing step that the fabricator must build into the route [S2].
Mechanical fields need the same treatment: list the load case (compression, bending, cantilevered), the maximum stress in MPa, and any creep or fatigue requirement; the design must use the lower strength of quartz (roughly 48 MPa tensile, 1100 MPa compressive for fused silica) rather than the compressive figure, and the RFQ should say which strength governs the structural check [S2]. For wet or acid service, name the chemical and concentration (for example, "5% HF, 60 degC, 4 hours"), because HF attacks all silica glass and the fabricator needs to know whether the part will be coated, used once, or reused; ambiguous chemical exposure is the most common reason a quartz RFQ bounces back for clarification [S3]. Buyers working on chemical material process gear should also call out any pH, halogen, or plasma exposure up front, since the same SiO2 grade that survives 1000 degC will etch rapidly in hot caustic.
Drawing Control, Inspection, and Documentation
Use ASME Y14.5 for dimensioning and geometric tolerancing on the quartz drawing, mark the controlling 2D file or 3D model, and state the revision level and revision date on the RFQ; without that, the fabricator cannot tell whether the 2025-08 drawing or the 2026-03 revision is the one to quote, and the order risks being built to the wrong version [S1][S4].
The inspection documents line should list exactly which records ship with the part: material certificate (mill cert), dimensional inspection report, surface roughness reading, optical transmission curve, and visual per scratch-dig; most quartz shops will include a cert by default, but a transmission scan or a CMM report is a paid extra and must be on the RFQ to be on the quote [S1][S2]. For buyers used to writing casting mold RFQs the same discipline applies: cert and report scope on the line, otherwise the lowest bidder quietly omits them and the actual cost lands as a change order at PO time.
Substitution Rules, Quantity, and What NOT to Do
A clean quartz RFQ states "no substitute without written approval" or "equivalent grade from alternate supplier acceptable if OH content, transmission, and dimensional tolerance meet spec"; the worst position is silence, because the fabricator will then either refuse to quote or quote a grade that is technically a substitute without flagging it [S1][S3].
Quantity, lead time, and delivery location belong on every RFQ regardless of material, and a useful pattern is "10 pieces prototype, 200 pieces within 12 months, delivery to City, State, 4 weeks from PO" because prototype and production runs use different fixturing and annealing ovens [S5]. Buyers should also avoid the two classic mistakes on quartz RFQs: writing "glass" instead of the specific silica family, and asking for a surface finish tighter than the dimensional tolerance supports; both produce a quote that does not reflect the real process. The "what not to do" list is short and the cost of getting it right is small relative to the cost of a structural quartz part that anneals unevenly or fails the first thermal cycle, so treat the spec like a controlled engineering document and the quote will come back clean the first time.