Funnels have a conical shape and short, wide stems for filling bottles or transferring powders. Filling funnels typically have a 60-degree angle that permits accurate fitting of filter paper, as well as vents or flutes to reduce vacuum formation and decrease filtering time.
Filling Funnel Materials
Borosilicate glass filling funnels include a strong beaded edge that resists chipping. Their resistant structure allows for the use of various reagents and chemicals. They also have a high resistance to thermal and mechanical shock and chemical attack. Funnels made from flint glass and soda-lime glass are also available.
Plastic filling funnels may be disposable or reusable and are made from polystyrene, polypropylene, polyethylene (LDPE or HDPE), or other resins.
Metal funnels are durable and reusable and may be constructed from a variety of metals. Each has characteristics that facilitate a particular use and purpose.
Filling funnels are available in a range of sizes and dimensions. They are typically sized based on capacity — the volume they can contain. Dimensionally, they may vary in top diameter, stem length, stem diameter, bowl angle, bowl capacity, and overall length. Filling funnels may be classified as Class A or Class B based on tolerances specified by ASTM and other standards.
What Different Types of Glass Funnels Are Available?
• General-purpose glass filling funnels for channeling, filling, and decanting liquids
• Short-stem or powder funnels to prevent the stem from clogging during the handling of fine powders
• Long-stem analytical funnels, often used with filter papers
• Fluted funnels to help reduce vacuums and facilitate more rapid filtration
• Büchner, glass-filtering, or vacuum filtration funnels made with an integral sintered glass disc for filtering precipitates or particulates without the need for filter papers. The sintered discs come in a range of pore sizes, typically from 10 to 40 μm
• Pear-shaped separatory funnels (separating or separation funnels) fitted with a stopper and a PTFE or glass stopcock for separating layered immiscible liquids in chemistry applications
• Weighing funnels to function as weighing dishes and to transfer weighed solids to other vessels