- 250 ml funnel with Glass key stopcock
- Made from high-quality 3.3 borosilicate glass
- Includes interchangeable polypropylene stopper
- 24/29 socket size
- Low temperature gradient – can withstand high temperatures and thermal shocks*
- Superior chemical durability
- Compliance with IS 1575.
- Cylindrical shape
OVERVIEW:
The GWSI 250 ml Graduated Dropping Funnel with Glass Stopcock and Socket is a semi-micro instrument built for the smallest bench-scale additions where every fraction of a milliliter matters and an all-glass flow path is essential. Formed from premium borosilicate 3.3 glass, it provides outstanding chemical inertness and high thermal shock resistance in a compact format that fits neatly onto micro-reactor and semi-micro distillation assemblies. The hand-lapped glass stopcock key delivers fine, controllable flow through a completely glass-on-glass seal, and the interchangeable ground joint socket ensures a vapor-tight connection in any matching taper setup.
HISTORY:
Semi-micro dropping funnels emerged from the microscale chemistry reform that swept through university teaching labs during the 1980s and 1990s. Pioneering educators argued that traditional large-scale practicals generated excessive waste and exposed students to unnecessary chemical hazards. Glassware manufacturers responded by producing fully functional miniature versions of every standard joint component — including 250 ml dropping funnels with matched glass stopcocks — so that students could learn the same techniques used in full-size Class A volumetric glassware and Class B glassware while working with just a few milliliters of reagent.
APPLICATIONS:
– Pharmaceutical discovery labs — dropwise addition of high-value intermediates during milligram-scale reaction screening
– Biotech enzymology labs — controlled delivery of co-factors and inhibitors into small-volume assay cuvettes
– Industrial fragrance and flavor labs — metered addition of concentrated aroma compounds during micro-formulation trials
– University microscale organic labs— green chemistry practicals using reduced solvent volumes and catalytic reagent quantities
– College analytical chemistry labs — micro-titrations and small-sample gravimetric determinations
– School advanced chemistry streams — safe, low-waste demonstrations of reaction kinetics and equilibrium using minimal reagents
– Research institutes — trace synthesis, radiolabeling, and isotope dilution studies requiring sub-milliliter addition accuracy
– Educational institutes — student training on semi-micro glassware assembly, glass stopcock technique, and responsible chemical use
MANUFACTURING PROCESS:
GWSI produces each 250 ml glass stopcock dropping funnel by melting high-purity borosilicate 3.3 glass at over 1,600 °C, then forming the miniature reservoir and stem through a combination of master hand-blowing for fine wall control and precision automated molding for repeatable dimensional accuracy. The tiny glass stopcock key and its matching barrel are individually lapped together using ultra-fine abrasive pastes to achieve a smooth, bubble-tight seal at this reduced scale. The socket joint is shaped using ceramic glass fusing for exact taper conformity, and the completed piece undergoes a controlled annealing cycle in a lehr oven to relieve all residual thermal stress.
TESTING PROCESS:
Every funnel begins with a meticulous manual inspection where technicians examine wall uniformity, miniature stopcock bore alignment, joint taper roundness, and fine graduation legibility under magnification. A Polariscope polarization stress test then verifies zero residual strain across the entire glass body and stopcock assembly — any birefringence pattern leads to immediate rejection. The volumetric graduation is validated on the basis of ISO and DIN standards using manual or automatic testing machines, and NABL gravimetric calibration certifies the scale to its declared Class A or Class B tolerance.
PRINTING PROCESS:
Fine graduation lines and small-format volume numerals are applied through precision screening with glass enamels — ultra-high-resolution ceramic inks designed for crisp marking on miniature borosilicate surfaces. The funnels are then fired in high-temperature kilns where the ceramic layer sinters and permanently fuses into the glass matrix, producing scale markings that resist chemical attack, abrasion, and repeated autoclave sterilization without any loss of definition.
PACKAGING PROCESS:
Each funnel passes through a final cosmetic sorting stage where inspectors reject any unit with surface imperfections, uneven walls, or stopcock irregularities. The miniature glass stopcock key is then secured to its matched barrel with a soft elastic band to prevent loss or mismatch during handling and shipping. Approved pieces are individually wrapped in shock-absorbing bubble wrap and packed in heavy-duty double-wall corrugated export boxes with custom cardboard inserts for safe transit worldwide.
MAINTENANCE & SAFETY:
– Grease the glass key with a barely visible film of laboratory-grade silicone stopcock grease — at this small scale, even a slight excess can block the narrow bore or contaminate reagents.
– Rinse immediately after use with warm deionized water, then wash with a mild non-ionic detergent; use a fine-tipped micro-brush to clear the miniature stopcock bore.
– Autoclave at 121 °C with the glass key removed from the barrel to prevent thermal seizure of the lapped surfaces; this autoclavable lab glass maintains full dimensional accuracy through repeated cycles.
– Store with a small paper slip between the key and barrel to keep the ground surfaces from cold-fusing during prolonged storage — this is especially important at semi-micro scale where surface contact is proportionally greater.
– Handle with extra care — the smaller wall thickness of 250 ml semi-micro glassware makes it more susceptible to chipping at the stem tip and joint rim if knocked against hard surfaces.
– Never force a stiff stopcock; soak the barrel in warm water to soften old grease, then ease the key free with gentle finger rotation — pliers or tools will almost certainly crack a semi-micro barrel.
Manufactured by GWSI Glass Lab — Ambala, Haryana, India (The Science City)