FAQ

This is where you can find frequently asked questions about DURAN® laboratory glass.
You can find more information under our Technical Information heading, in the DURAN® -Laboratory Glassware Catalogue or by contacting us.

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Up to what maximum temperature can DURAN® be used?

The maximum permissible operating temperature for DURAN® is +500 °C. Above a temperature of +525 °C the glass begins to soften and above a temperature of +860 °C it changes to the liquid state.

Category: Laborglas
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What temperature variations can DURAN® sustain?

As it has a very low coefficient of linear expansion (α = 3.3 · 10–6 K–1) a feature of DURAN® is its high thermal shock resistance up to ΔT = 100 K.

Category: Laborglas
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What is the lowest temperature to which DURAN® can be cooled?

DURAN® can be cooled down to the maximum possible negative temperature and is thus suitable for use with liquid nitrogen (approx. – 196°C). During such use/ freezing, the effect of the expansion of the content must be borne in mind. In general DURAN products are recommended for use down to – 70 °C. When doing so, bear in mind the product geometry and the properties of any accessories used (e.g. screw caps). When cooling down and thawing ensure that the temperature difference does not exceed 100 K.

Category: Laborglas
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How chemically resistant is DURAN®?

Glass is the most universal material in terms of chemical resistance when compared with other materials.

DURAN® borosilicate glass 3.3 is highly resistant to water, acids, saline solutions, organic substances and also halogens such as chlorine and bromine. Its resistance to bases is also relatively good. Only hydrofluoric acid, concentrated phosphoric acid and strong bases cause appreciable surface removal of the glass (glass corrosion) at high temperatures (>+100 °C).

In detail:
Water resistance:
DURAN® corresponds to Class 1 of the glasses that are divided into a total of 5 water resistance classes in accordance with ISO 719 (98 °C).

Due to its good water resistance, DURAN® meets the requirements of the USP and EP for a neutral glass or corresponds to glass type 1 and can be used in an almost unrestricted way in pharmaceutical applications and in contact with foodstuffs.

Acid resistance:

DURAN® corresponds to Class 1 of the glasses divided into 4 acid classes in accordance with DIN 12 116.  As the surface removal after boiling for 6 hours in normal HCl is less than 0.7 mg/100 cm2, DURAN® is classed as acid-resistant borosilicate glass.

Resistance to bases:
DURAN® corresponds to Class 2 of the glasses divided into 3 base classes in accordance with DIN ISO 695.
Only strong bases combined with high temperatures (>+100 °C) cause appreciable surface removal of the glass.

Category: Laborglas
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What is the difference between DURAN® and soda-lime glass?

DURAN® is a borosilicate glass 3.3. The coefficient of linear expansion, 

α= 3.3 x 10–6 K–1. This means that the glass expands by some 3.3 x 10-6

length units per Kelvin, over a temperature range of +20°C to +300°C.

The smaller the linear expansion coefficient, the more resistant the glass is to temperature variations.

At larger expansion coefficients (compare the linear coefficient of expansion for soda lime glass, α= 9.1 x 10–6 K–1), the temperature difference during heating causes stresses in the glass and thus possible breaking.

Category: Laborglas
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How high is the chemical and thermal resistance of soda-lime glass?

Soda-lime glass is a clear glass belonging to the third water resistance class (compare DURAN® resistance class 1).

Due to its high heat expansion (coefficient of linear expansion, α= 9.1 x 10–6 K–1), the resistance of soda lime glass to temperature changes is small (ΔT = 30 K).

A maximum usage temperature of +100°C is recommended.

Category: Laborglas
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Can DURAN® be used in the microwave?

DURAN® laboratory glassware is suitable for use in microwaves. This also applies to plastic coated DURAN® products.

Category: Laborglas
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How can the nominal diameter (DN) be determined or measured?

To determine the DN, the diameter of the sieve plate or the outside diameter of the flange can be measured. Using the tables on the product pages of the DURAN laboratory glass catalogue, these values can be matched to the corresponding DN.

Category: Laborglas
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How accurate are the printed scales on general DURAN® laboratory glassware items? (Beakers, Erlenmeyer flasks, laboratory bottles)

For DURAN® beakers, Erlenmeyer flasks, laboratory bottles, etc., a scale accuracy of ± 10% is attained for the bottom and top scale markings.

I.e. the products are not suitable for use as volumetric glassware.

Category: Laborglas
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What does APPROXIMATE VOLUME mean?

Approximate volume means that the volume filled up to a particular scale marking is approximately equal to the indicated volume. For an exact determination of the volume, DURAN® volumetric glassware should be used.

Category: Laborglas
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Is general DURAN® laboratory glassware certified (DIN/ISO)?

Our company is certified to DIN EN ISO 9001 by TÜV.

 

Alongside the international standard DIN/ISO 3585, in which the properties of borosilicate glass 3.3 are defined, all DURAN® laboratory glassware corresponds to the standards for glass laboratory apparatus. The relevant DIN/ISO standard is given on the product pages of the laboratory glassware catalogue.

Category: Laborglas
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Are product specifications/certificates available for DURAN® products?

Information relating to the glass is held in a glass specification, which is available upon request.

DURAN® laboratory glass bottles, Erlenmeyer flasks and beakers are provided with a retrace code. Using the eight-character code and the corresponding article number, the batch and quality certificate (link to batch cerificate search form) for DURAN® laboratory glass bottles, beakers, Erlenmeyer flasks and premium caps can be obtained at any time.

Category: Laborglas
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What is the temperature resistance of the plastic-coated laboratory bottles?

The maximum operating temperature is +135 °C and thus the bottle is suitable for use in an autoclave. Long-term exposure to temperature (> 30 minutes) should be avoided. DURAN® Protect bottles can be used for freezing (– 30 °C) and used in microwaves.

Category: Laborglas
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What different types of NMR tubes are available?

NMR tubes are available, according to requirement, in three accuracy classes (economic, professional and scientific). The correct tube can be selected according to magnetic field and spin.

The caps for NMR tubes are sorted by colour and enclosed with the tubes:

DURAN® economic – pack of 250, caps: 50 each of red, yellow, blue, green, black DURAN

DURAN® Professional – pack of 250, caps: 50 each of red, yellow, blue, green, black DURAN

DURAN® Scientific - pack of 5, already provided with blue cap. The caps are also available separately.

Category: Laborglas
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Are DURAN® products suitable for working under pressure and vacuum?

Only the extra designated products are, due to geometry and wall thickness, suitable for working under pressure/vacuum (e.g. filtering flasks, desiccators or flat flange vessels).

Category: Laborglas
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Are DURAN® laboratory bottles suitable for working under pressure and vacuum?

In general, DURAN® laboratory bottles are not designed for pressure and vacuum applications.

For pressure applications using laboratory bottles, the DURAN® pressure plus bottle should be used. This is pressure resistant from -1 bar to +1.5 bar due to a modified geometry and increased wall thickness.

The plastic coating of laboratory bottles (DURAN® protect) has no influence on pressure resistance, these products are not designed for use under pressure.

Category: Laborglas
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To what maximum vacuum can desiccators / filtering flasks be loaded?

DURAN® desiccators/ filtering flasks can be used up to the maximum technically possible vacuum, however they are not designed for use under positive pressure.

Category: Laborglas
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What is the manufacturing procedure for amber DURAN® laboratory bottles or what is the effect of the amber colouring on the properties?

To colour the article an innovative spraying process uses a special medium-diffusion ink solely on the outside of the clear glass.

Consequently an extremely uniform amber colour is achieved. Finally, the coating is baked on and is thus resistant to chemicals and cleaning in a dishwasher. 

The proven DURAN® properties within the bottle remain unaffected and any interaction between ink and content is excluded.

Category: Laborglas
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What is the max. rpm that DURAN® centrifuge tubes can be used at?

The centrifuge tubes are approved in accordance with DIN 58 970 (Part 2) up to a maximum relative centrifugal acceleration RZB = 4000 and for filling up to their capacity with contents having a maximum density of 1.2 g/ml.

Calculation:  RZB = 1,118 x 10–5 x r x n2

n = sqrt [4000/(1,118 x 10-5 x r)]

Category: Laborglas
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Can DURAN® glass be disposed off in a waste glass recycling facility?

DURAN® laboratory glass should under no circumstances be disposed of in normal bottle banks, since its high melting point can create problems if it is mixed with other glass cullet (soda-lime glass) for recycling. The customer is responsible for correct disposal, in principle this means disposal with general household waste (residual waste) in accordance with the relevant guidelines, provided, however, that the glass is quite free of any harmful contamination.

Category: Laborglas
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Can DURAN® be ordered directly from the DWK Life Sciences GmbH?

The complete DURAN® laboratory glassware range is distributed exclusively through specialist laboratory dealers. You can find a dealer in your vicinity by clicking here or by contacting us.

Category: Laborglas
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Where can I find more information?

You can find more information under our Technical Information heading, in the DURAN® -Laboratory Glassware Catalogue or by contacting us.

Category: Laborglas