Quick Answer
A quartz flask is a high-purity fused silica vessel with a neck. The neck is the point. It takes a stopper, a ground joint, a condenser, or an inert-gas line, so the contents can be heated, refluxed, distilled, or held under vacuum without the open-top losses of a beaker.
It is not a quartz beaker. A beaker is for open heating, mixing, and pouring. A flask is for closed or semi-closed work: Erlenmeyer (conical) for swirling and digestion, round-bottom for uniform heating and distillation, multi-neck for synthesis with several connections at once. FGQuartz fabricates these forms to drawing or sample — including joint size, neck count, and wall thickness — with no minimum order quantity. Send the volume, neck layout, and joint specification and we reply within 24 business hours.
Key Takeaways
Use a flask when the process needs a neck. Use a beaker when it does not. Ordering the wrong one is the usual first RFQ mistake.
Three shapes cover almost every laboratory drawing: Erlenmeyer (conical), round-bottom, and multi-neck. Volumetric flasks are a fourth, custom geometry when a calibrated volume mark is required.
Quartz is chosen over borosilicate when the temperature, acid purity, or contamination budget exceeds what soda-boron glass can hold — not as a default substitute for every flask on the bench.
Ground-joint size (14/20, 19/22, 24/40, 29/42 and others) belongs on the drawing. “Standard neck” is not a specification.
Quartz resists most mineral acids and organics. It is attacked by hydrofluoric acid, hot concentrated phosphoric acid, and strong alkalis at high temperature. Do not specify quartz for HF service.
For RFQ, send flask type, nominal volume, neck count, joint size, bottom shape, and a sketch or sample. One prototype is acceptable.
What a Quartz Flask Is — and What It Is Not
A flask is laboratory ware with a reduced opening. That opening is formed, ground, or flanged so other apparatus can join it. Everything else — wall thickness, bottom radius, optical clarity — is secondary to that joint.
FGQuartz makes flasks as laboratory quartz components, flame-formed and annealed from high-purity fused silica. They sit in the same family as beakers, evaporating dishes, and reaction tubes, but they are specified differently.
A quartz flask is not a spectrophotometer cell. Light-path accuracy belongs on a cuvette drawing, not on a flask. It is not a disposable culture flask for microbiology; those are borosilicate or polymer for a reason. It is not a crucible: a crucible is an open cup for ashing, melting, or crystal growth, with no neck.
If the work is open-top heating and pouring, order a beaker. If the work is reflux, distillation, inert-gas blanketing, or vacuum, order a flask. If the work is ignition of a solid, order a crucible or an evaporating dish.
When Quartz Instead of Borosilicate
Most laboratory flasks in the world are borosilicate. Quartz costs more and is used when borosilicate is the wrong material.
Temperature. Fused silica handles continuous service in the same band as other quartz glass labware, typically up to about 1100–1200 °C depending on wall thickness and atmosphere. Borosilicate softens far below that. If the flask sits in a high-temperature mantle, a tube furnace vestibule, or a digestion that runs well above 500 °C, quartz is the default.
Purity. Trace-metal leaching from borosilicate sodium and boron is unacceptable in some acid purification, semiconductor wet chemistry, and low-blank analytical prep. High-purity fused silica keeps the blank low. That is why quartz flasks show up next to sub-boiling stills and ultra-pure acid handling, not next to general teaching labs.
Thermal shock. Quartz has a very low coefficient of thermal expansion, so a well-annealed flask survives faster temperature changes than borosilicate of the same geometry. It is not indestructible. A thick multi-neck with an unannealed weld will still crack. Specify anneal after flame work.
Chemistry. Quartz is inert to hydrochloric, nitric, and sulfuric acids and to most solvents used in synthesis. It is the wrong choice for hydrofluoric acid and for hot caustic. If the process uses HF, say so in the RFQ so we do not quote quartz into a failure.
Quartz Flask Types FGQuartz Manufactures
We do not stock a catalog of flask SKUs. Geometry follows the drawing. The three forms below cover nearly every laboratory RFQ. A fourth — volumetric — is made when the print calls for a calibrated mark.
Erlenmeyer quartz flask (conical)
Wide base, sloping walls, narrow neck. The shape is for swirling without wetting the joint, and for sitting stably on a bench or hotplate. Quartz Erlenmeyer flasks are used for acid digestion, high-purity mixing, and heating of aggressive reagents that would attack or leach borosilicate.
They are not the first choice for distillation: the conical shoulder does not present a uniform boiling surface, and bumping is harder to control than in a round-bottom. They are also a poor substitute for a beaker when you need a pouring spout and a wide mouth for a spatula.
Specify: nominal volume, neck finish (plain, tooled, or ground joint and size), wall thickness if it matters, and whether the base must sit flat on a hotplate. A slightly flattened bottom is a fabrication note, not a round-bottom flask.
Round-bottom quartz flask
Spherical body, one neck. This is the distillation and reflux flask. A heating mantle cups the sphere and heats the contents evenly. That is the opposite of a flat flask on a hotplate, which heats through a small contact patch. Do not specify round-bottom and then expect it to stand unsupported on a ceramic plate — it needs a cork ring, a heating mantle, or a clamp.
Round-bottom quartz flasks are the usual vessel for high-temperature distillation, solvent stripping of corrosive mixtures, and reactions that must be heated uniformly. The neck takes a still head, a condenser, or a stopper. Joint size and neck length decide whether standard glassware will mate; if the rest of the train is borosilicate, confirm that a quartz joint of the same taper will seat. It will, if the taper is ground to the same specification.
Specify: volume, joint size, neck length, and whether a short-neck or long-neck form is required. If the flask is used under vacuum, say so — wall thickness and anneal are not optional on that drawing.
Multi-neck quartz flask
Two, three, or four necks on a round-bottom body. One neck for a condenser, one for a thermometer or thermocouple well, one for an addition funnel or inert-gas inlet. This is a custom quartz fabrication job: each neck is flame-welded, the joints are ground, and the assembly is annealed as a whole.
The welds are the failure points. A three-neck flask that cracks in service almost always fails at a neck-to-body joint, not in the sphere. If you are replacing a broken flask, send the failed piece. We copy the neck angles and increase anneal control rather than guessing from a photo of a catalog borosilicate flask.
Specify: body volume, number of necks, joint size on each neck (they are often not identical — center 24/40, sides 19/22 is common), neck angles, and angled versus vertical side necks. “Three-neck flask” without joint sizes is not a quoteable print.
Volumetric and other custom flasks
Calibrated volumetric flasks, Kjeldahl-style long necks, and flasks with extra side arms are made to print. Volumetric work in quartz is uncommon but justified when the liquid cannot see borosilicate and the volume still has to be known. Put the calibration temperature and the tolerance on the drawing; do not assume a borosilicate Class A spec transfers without restatement.
Quartz Flask vs Quartz Beaker
The two are adjacent on a laboratory quartz RFQ and they are not interchangeable.
Order a beaker for open heating, mixing with a rod, pouring, and short-term holding. The wide mouth is the feature. Order a flask when vapor must be returned (reflux), removed (distillation), or excluded (inert gas, vacuum), or when a stopper must sit during a hold at temperature.
A conical flask is not “a beaker with a neck.” Swirling an Erlenmeyer is not the same as pouring from a beaker spout. If technicians will add solids with a spatula, a flask neck will fight them; use a beaker or a wide-mouth bottle geometry instead.
Our quartz beaker guide covers open vessels. This page stops at the neck.
Joints, Necks and What Goes on the Drawing
Most mismatches happen at the joint, not at the silica grade.
Ground taper joints must list the size: 14/20, 19/22, 24/40, 29/42, or the equivalent your apparatus already uses. Inner (female) versus outer (male) belongs on the print. A quartz inner joint mating to a borosilicate condenser of the same size is normal; the taper standard is the interface, not the glass type.
Plain tooled necks take a rubber stopper or a PTFE plug. They are cheaper to make than a ground joint and wrong if you need a condenser train.
Flanged or cup necks show up on some high-purity and vacuum assemblies. They are custom. Send a sketch.
Neck length matters when a heating mantle, a clamp, or a furnace opening has to clear the joint. Measure the existing flask, including the distance from the joint to the sphere.
Wall thickness is a strength and thermal-mass choice. Heavy wall survives vacuum and clumsy clamps; it also heats slower and costs more silica. Do not specify heavy wall “to be safe” on a flask that only sees atmospheric acid digestion.
How Quartz Flasks Are Made
Laboratory flasks are hot work. Tube or blown stock is shaped over an oxy-hydrogen flame, necks are pulled or welded on, joints are ground, and the piece is annealed to drop residual stress. That sequence is the same thermal processing used on other custom quartz assemblies, scaled to flask geometry.
CNC belongs on the joint grind and on any flat that must sit on a hotplate. It does not replace flame forming for a spherical body.
Fire polish on the inner surface reduces particles and makes cleaning realistic. A ground inner wall that is never fire-polished will hold residue and shed silica fines into the first high-purity run.
If you send a borosilicate catalog flask and write “same, in quartz,” we can copy the envelope. Confirm joint standard, volume, and whether vacuum service applies. Quartz shrinks and draws differently from borosilicate in the flame; a blind copy without anneal data is how copies crack on the first heat-up.
Applications That Actually Use Quartz Flasks
High-purity acid handling and digestion, where borosilicate blank is too high and PTFE cannot take the temperature.
Distillation and reflux of corrosive or ultra-clean mixtures, including feed flasks on sub-boiling stills. The still head and condenser may be quoted as a set; the flask is still specified as its own line.
High-temperature synthesis under inert gas or vacuum, using a multi-neck body so the condenser, addition line, and temperature probe do not share one joint.
Sample prep for trace analysis, when the vessel sees hot mineral acids and the next step is ICP or similar low-blank measurement. This is vessel purity, not torch design.
Pilot-scale chemistry that has already outgrown a test tube but is not yet a lined metal reactor. Volumes we see most often run from tens of millilitres to about two litres. Larger is possible; it is a different handling and annealing problem, so put the volume on the RFQ early.
We do not recommend quartz flasks as drop-in replacements for biological shaker flasks, media bottles, or UV-Vis sample cells. Wrong geometry, wrong cost, wrong cleaning cycle.
Common Problems
Crack at a side neck after the first heat cycle: residual weld stress. Send the failed flask. The replacement should be annealed as an assembly, not as a body with necks added later and shipped.
Joint leaks under vacuum or reflux: taper not held, or a quartz joint mixed with a damaged borosilicate counterpart. Specify the joint standard and inspect the mating piece.
Flask will not sit on the hotplate: you specified round-bottom and expected a beaker. Use a mantle, or specify a flattened Erlenmeyer base.
Clouding or wall thinning in service: chemistry, often fluoride or hot alkali, not a “bad batch of quartz.” Change material or change the process. Quartz will not survive HF.
Particles in the first high-purity fill: inner surface left ground. Specify fire-polished ID and clean packing.
Volume “not what we use in glass”: quartz copies follow the drawing, not the catalog nickname. A “500 ml flask” must have a target brim or working volume on the print.
What to Order
Open heating and pouring: order a beaker, not a flask.
Swirling, digestion, or hotplate work with a neck: order an Erlenmeyer quartz flask, and say whether the base must sit flat.
Distillation, reflux, or heating-mantle work: order a round-bottom quartz flask and the joint size that matches the still head.
Synthesis with condenser plus probe plus addition line: order a multi-neck flask with each joint called out. Do not order three single-neck flasks and expect to manifold them in silicone hose.
Ashing or melt: order a crucible or dish, not a flask.
If the flask is one piece of a still or digestion train, quote it with the matching heads and condensers rather than as an isolated catalog item. The joint is the interface; the set is what the lab actually runs.
Request a Quartz Flask Quote
A quartz flask is a neck, a volume, and a thermal cycle. Get those three right and the silica grade is the easy part.
FGQuartz has manufactured high-purity fused silica laboratory and process components in Lianyungang since 2005, including Erlenmeyer, round-bottom, and multi-neck flasks made to drawing or reverse-engineered from a sample. Send the type, volume, joint sizes, and the process temperature — or the broken flask — and the review comes back as a manufacturable part.
Request a manufacturing quote. We respond within 24 business hours.