Quick Answer: The Specimen Jar, Round with Ground Flange and Knobbed Stoppers is a cylindrical jar whose rim is ground flat to seat a close-fitting cover with a knob for lifting. A round specimen jar of this design can be opened and resealed repeatedly, so preserved specimens can be taken out for study and returned.
How the Ground Flange Seals
A ground flange is a wide, flat rim whose top surface has been ground so that it is slightly rough and perfectly level. The matching cover, here with a knob on top, has a ground underside, so the two surfaces meet closely all the way round. A thin smear of petroleum jelly or silicone grease on the flange fills the fine roughness and makes the joint close to airtight, which slows the evaporation of preserving fluid while still letting the cover lift off by hand.
That combination suits teaching collections. Unlike sealed museum jars, a flanged jar can be opened whenever a specimen is needed for a practical, drained, examined in a dissecting tray and returned to fresh fluid. Round jars are also easy to wipe, strong for their weight and suited to specimens that sit upright, such as a coiled snake or a sectioned organ. The curved wall does magnify a little, so for photographs and display the flat-sided rectangular specimen jar gives a truer view.
The same ground flange principle is used on the gas jar with ground flange, where a greased glass cover retains a gas. The listing does not state the jar’s material, capacity or whether the cover is glass.
Care & Handling
- Keep a very thin, even layer of grease on the flange; too much smears onto the specimen and attracts dust.
- Lift the cover straight up by its knob and place it ground side up on a clean cloth.
- Wipe the flange clean before replacing the cover, since grit on ground surfaces spoils the seal and scratches the glass.
- Handle formalin and other preservatives with gloves in a ventilated area.
Applications
- Teaching collections of preserved animals and organs used in dissection practicals
- Storing fixed tissue samples in formalin before processing
- Holding botanical specimens in preserving fluid for class study
- Dry storage of bones, shells or seeds that should stay dust-free
Specifications
| Item | Specimen jar, round |
| Rim | Ground flange for a close-fitting cover |
| Cover | Knobbed stopper or lid, lifted by hand |
| Sealing | Ground surfaces, usually lightly greased |
| Material, capacity and cover material | Confirm at enquiry |
Why Choose LabEquip
Schools and colleges that bring preserved specimens out for regular practicals choose flanged jars that open without breaking a seal. LabEquip lists them in Biology Lab Products; ask about capacity and cover type through the contact page.
Frequently Asked Questions
What is a ground flange?
It is a wide rim ground flat and slightly rough so that a cover with a matching ground surface fits closely. With a thin film of grease the joint becomes nearly airtight.
Why grease the flange?
Petroleum jelly or silicone grease fills the fine roughness of the ground glass, making the seal tighter and reducing evaporation of the preserving fluid.
How is this jar different from a sealed museum jar?
Museum jars are usually sealed permanently for display, while a flanged jar with a lift-off cover can be opened and closed as often as needed, which suits specimens used in practicals.
Why does the specimen look larger through a round jar?
The curved glass and liquid act like a lens and magnify the specimen slightly. Flat-sided rectangular jars avoid this distortion.
Can the jar store dry items?
Yes. It is also used for dry bones, shells, seeds and similar items that need to be kept free of dust and insects.
What capacity and material is the jar?
Round specimen jars are made in several sizes, usually in glass. The listing does not state the capacity or cover material, so confirm them when you enquire.
Last Updated: September 2026
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