Scientific Glass Blowing Supplies

Enhance efficiency and convenience with scientific glass blowing supplies from DWK.

At DWK, we understand that, despite our extensive catalog, some scientific endeavors require custom glassware created by your own scientific glassblowers. To enable these efforts, we offer a broad range of scientific glass blowing supplies, including flanges, blanks for lids and vessels, stirrer shafts, bearings, and other essential tools for manufacturing customer-specific pilot plants, bioreactors, wiped film evaporators, or distillation apparatus. These scientific glass blowing supplies include blanks, such as separating or dropping funnels and evaporating flasks, which are ideal for master glassblowers who would like a grease-free operational experience.

Supporting Scientific Glassblowers

Most laboratory glass apparatus consist of several individual components. And at some point, pumps, thermostats, thermometers, and measuring electrodes all have to be connected. We understand that those connections must adhere to safety, tightness, chemical, thermal, and mechanical resistance requirements. That’s why we’ve compiled a range of connectors to help you fulfill your customers’ specific needs. Because we know that certain instances demand that you work without grease, each product group has grease-free options. In addition to offering components for connection, our scientific glass blowing supplies also include closures and accessories for securing connections.

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One of the main functions of laboratory equipment is to regulate gas or liquid flow, whether it’s a simple separating funnel or a complex Schlenk line for the high vacuum range. Choosing the right components is vital to ensuring the flawless function of the final product made by the scientific glassblower. Here’s a quick guide to help you choose the right scientific glass blowing supplies:

  • Budget -> GU-Valve
  • Budget -> massive plug
  • Dosing function -> Valve
  • Free of grease -> PTFE-key
  • HV range -> PRODURAN®
  • Open and close -> Single way stopcock
  • Schlenk line -> 2 Way Stopcock
  • Special applications -> 3 Way Stopcock
  • Temperature change-> Hollow plug
  • Vacuum -> Taper 1:5

For greaseless applications in processes involving temperature changes, stopcocks with PTFE plugs are not the preferred choice. Because PTFE has a much higher thermal expansion when compared with DURAN®, temperature changes may lead to decreasing tightness. In such cases, the glass blowing supplies we recommend are spindle valves (PRODURAN®, GU-Valves).

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Our filter discs are made of DURAN® glass to ensure no additional stress occurs when a filter is fused to a DURAN® tube. Permanent stress inevitably results when working with two pieces of glass with different material properties, such as the coefficient of thermal expansion (α) and the transformation temperature (Tg), increasing the demands of an already challenging working process.

The pore size of sintered glass filters is controlled by the grain size of the glass powder used and by the settings of the sintering process. Here at DWK Life Sciences, the frits' pore size and mechanical strength are subject to strict quality control. You’ll find helpful diagrams regarding the flow rates for fluids and gas and further technical information here.

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We provide off-the-shelf laboratory glassware, which includes flasks, beakers, and separating funnels, meeting the needs of many standard applications. But we know that your needs may require custom-built products. That’s why, complementing our catalog of laboratory supplies, we offer blanks for further processing by scientific glassblowers. These blanks can be used for creating separating or dropping funnels, evaporating flasks, and other glassware. You can trust that the blanks are made with consistently uniform wall thickness, which is crucial for your success. We recognize that wall thickness deviations increase the glass's thermal stress, resulting in a higher risk of breakage.

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For reaction vessels and plants carefully constructed according to your needs, we provide a standardized product range. And while we often supply products to the end user, we recognize that there’s also demand for tailored solutions to the final customer. That’s where scientific glassblowers step in, using our wide range of flanges, blanks, stirrer shafts, bearings, and other accessories to manufacture customer-specific pieces such as those required for pilot plants, bioreactors, wiped film evaporators, and distillation apparatus.

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DWK Life Sciences offers a comprehensive range of volumetrics. Pipettes, burettes, mixing and measuring cylinders, and measuring flasks are all available in various sizes, models, and accuracy classes. As with our other segments, we also offer blanks as part of our scientific glass blowing supplies. Our catalog includes unprinted, ungraduated items for manufacturing customized volumetric products. We achieve tight tolerances for semi-finished products by using high-quality raw materials like the DURAN® tubes with a limited tolerance range. This reduces costs and facilitates subsequent processing.

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Frequently Asked Questions

Glass blowers use many different materials which include glass that offers high resistance to thermal expansion and chemical corrosion, a furnace as the heating source, and protective equipment for safety. Other common glass blowing supplies include:

  • Blanks as the starting material to craft custom glassware
  • Hollow glassware with an empty interior space to provide containment for liquids and gasses
  • Joints, closures, and connectors for securing connections
  • Reaction vessel components which help to facilitate chemical reactions
  • Sintered glass filters carry out filtration processes and ensure that no additional stress occurs when a filter is fused to a tube
  • Stopcocks and valves to regulate the flow of gas or liquid

Hand-blown glass, custom-made by a scientific glass blower, is most suited when standard scientific glassware does not meet specific requirements. With hand-blown glass products, scientific glass blowers can modify standard scientific glassware or create bespoke designs to satisfy the unique needs of the research.

It’s important to understand that roughness cannot be defined by the grain size used in the grinding process. Parameters like the rotational speed, the grinding fluid used, and the contact pressure impact the resulting surface properties. For this reason, the requirements for surface quality according to international standards and our specifications refer to the arithmetical roughness of the surface (Ra).

DWK Life Sciences uses various methods for grinding — including diamond tools, silicon carbide, manual operations, and fully automated processes, depending on the type of product, the lot size, and the requirements.

First, a word of caution: broken glass is sharp-edged, and there is always a risk of injuries, even for experts.

To safely disconnect wedged joints, ask a colleague for help. Carefully pull the cone and the socket apart — no excessive force, as the glass may break at any time. While pulling, ask your colleague to shatter the joint by tapping on one of the tubes beside the connection. Use something similar to a ball-peen, made of wood or plastic — not metal — and be very cautious. If possible, turn the connection and tap from all sides. If there is no space to tap on one of the tubes, consider tapping on the joint. In this case, you have to be even more careful. Do not increase the force when the joints do not disconnect. Successfully separating a frozen joint is a matter of finesse, not strength.

Take a look at the question and answer below about avoiding “frozen joints” to learn how to avoid this situation going forward.

Here are some general guidelines to avoid “frozen” joints:

  • Always use either vacuum grease or PTFE sleeves.
  • Disconnect all joints when the apparatus is not in use.
  • Never put a cold cone in a hot socket.
  • Ensure the joints stay lubricated when working with fat solvent.
  • Remember that wet joints tend to stick, particularly when wetted by alkaline solutions.

You can minimize leakage and secure an excellent efficacy rate through meticulous handling and optimizing certain factors despite challenges in attaining a 100% tight seal. These factors include the properties of the cone and socket, such as the joint’s roughness, taper's accuracy, and roundness. By focusing on these attributes, you can ensure a practical tightness, even in the most demanding conditions, promoting longer-lasting and more reliable use in incandescent lamps and neon tubes.

Appropriate usage of vacuum grease and the correct use of the retaining device are essential for achieving a minor leakage rate. For these reasons, the DIN-standard 12 256 (tightness test of conical joints and stopcocks) refers to unlubricated joints to make measurements comparable. The requirement for the leakage rate according to DIN 12 540 and 12 541 is: ≤ 0,1 mbar l/s -1 . While this is not a high-level value, the leakage rate of lubricated stopcocks is better by orders of magnitude. However, for the reasons stated above, it is impossible to give a universally valid specification of the leakage rate of lubricated stopcocks. Generally, we recommend using valves for requirements to the leakage rate ≤ 10 -3 mbar l/s -1 . For PRODURAN® valves, we guarantee a leakage rate ≤ 10 -6 mbar l/s -1.

KECK™ clips — which ensure a safe connection — are available for conical and spherical joints and are easy to attach and loosen. For even stronger connections, we recommend using safety joints. This type of connection offers a much higher retention force and provides a system to release “frozen” joints.

Note: Please consider that contrary to KECK™ clips, safety joints will not release overpressure. When using safety joints, you must ensure that your apparatus is either resistant to pressure or that you use a pressure relief valve.

Sizes of ground joints are generally specified by two numbers, separated by a forward slash.
The first number represents the ground area's largest diameter (mm). For many sizes, the nominal size is a shortcut for the real size, like NS 19 (stands for 18,8mm) or NS 29 (29,2mm). The second number stands for the projection of length of the ground zone.
Example: NS 14 / 23
largest diameter (d): 14,5 mm
length (l): 23,0 mm
taper: 1:10
smallest diameter 14,5 – 23/10 = 12,2 mm