Business products: GLINDEMANN® PTFE Sealing Rings 
for taper joints (laboratory glassware).
PTFE is equivalent to Teflon
® from DuPont.

Home (English)      Business products: Glindemann PTFE Sealing Rings    Academics - Scientific Publications Dietmar GLINDEMANN
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News
Worldwide customers: "Glindemann PTFE Sealing Rings" are sold by Sigma-Aldrich.
Search Sigma-Aldrich web-shop for "glindemann" or enter Sigma-Aldrich catalogue number

Please contact Dr. Glindemann at dglinde@aol.com if you currently experience ordering problems.

Lowest prices in Europe:
Glindemann PTFE Sealing Rings
As low as 21.28 €/pack of 50 rings
Lab Logistics Group LLG in all European countries
http://www.llg-international.eu/en/partners-by-country.html
http://shop.llg.de/info6530_Dichtringe_PTFE_fuer_Kegelschliffe_lang_de.htm

Example LLG's partner Mercateo in all European countries http://www.mercateo.com/p/163-9011664/Dichtringe_fuer_Kegelschliffe_PTFE_NS_14.html

As low as 21.28 €/pack for a minimum of 4 packs

 

GLINDEMANN®-PTFE sealing rings  Image29.gif (1672 bytes)
for ground taper (conical) joints
Contact:
Dr. Dietmar GLINDEMANN
Goettinger Bogen 15
D-06126 Halle
Germany
ph:  0345  6879948 (country code 49)
(from the USA/Canada: dial 011 49 345 6879948, else dial 00 49...)
fx:   0345  6871333   (country code 49)
e-mail dglinde@aol.com
Internet : www.glindemann.net   


Links in this site:
Distributors and catalogue numbers of Glindemann Sealing Rings
Delivery and Prices of Glindemann Sealing Rings
Application: For what are
Glindemann Sealing Rings good for?
Procedure: Instruction on how to apply Glindemann Sealing Rings
Frequently asked questions and Know How on Glindemann Sealing Rings
Test reports on Glindemann Sealing rings (references)
Links on laboratory glass ware in the internet and to www.glindemann.net:

List of distributors of GLINDEMANN® sealing rings and their catalogue numbers
(to find distributor addresses in single countries, see next table)
Joint maximum diameter / mm 7 10 12 14 19 24 29 34 45 70 Distribution in
Glindemann Catatalogue No  K7 K10 K12 K14 K19 K24 K29 K34 K45 K70  
Number of Sealing rings /  unit  (pck) 50 50 50 50 50 50 50 50 50 50  
Distribution worldwide by SIGMA-ALDRICH (click link to find addresses for over 200 countries worldwide).  
Search for "glindemann" or enter Sigma-Aldrich catalogue number below.
Sigma-Aldrich Labware Catalogue)   Z50,198-0 
(Z501980)
  Z50,208-1
(Z502081)
Z50,220-0
(
Z502200)
Z50,231-6
(Z502316)
Z50,241-3
(Z502413 )
  Z50,252-9
(Z502529)
  Worldwide 200 countries
Distribution in USA, Canada, Mexico by Sigma-Aldrich.
Starting November 2009, customers of VWR, Fisher Scientific, Thomas Scientific use Aldrich-catalogue numers.
Please contact Dr. Glindemann at dglinde@aol.com if you currently experience ordering problems.
Distribution in Australia and Europe
LABGLASS Pty Ltd GSR7 GSR10 GSR12 GSR14 GSR19 GSR24 GSR29 GSR34 GSR45 GSR704 Australia, Oceania
AJ Cope & Son Ltd,
on-line shop    Thelabwarehouse.com
      QZZ27/14 QZZ27/19 QZZ27/24 QZZ27/29 QZZ27/34 QZZ27/45   UK, Ireland
Carl Roth GmbH, link to 28 Europ. countries     T221.1 E699.1 E700.1 E701.1 E702.1   T222.1   Europe (worldwide)
Fisher-Scientific
in Germany
10125930
(3391345)
10268410
(3391346)
10228460
(3391347)
10636521
(3391348)
10782131
(3391349)
10646521
(3391350)
10390001
(3391351)
10257790
(3391352)
10686901
(3391353)
  Germany, Austria, Switz.
VWR International in Germany 2016251 2016252 2016253 2016256 2016258 2016260 2016262 2016263 2016264 2016266 Germany, Austria, Switz.
Lab Logistics Group (LLG)  (Mercateo), link to many countries and distributors   9.011 663  

9.011 664

9.011 665 9.011 666 9.011 667

 

 9.011 668

  Europe (worldwide)
LR. Vetter Laborbedarf e.K. DKA-7 DKA-10 DKA-12 DKA-14 DKA-19 DKA-24 DKA-29 DKA-34 DKA-45 DKA-70 Germany
AMSI-Glas AG 6.300.007 6.300.010 6.300.012 06.300.014 06.300.019 06.300.024 06.300.029 6.300.0344 6.300.045 6.300.070 Switzerland

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Addresses of distributors, in countries, worldwide,
(to find catalogue numbers, see table above)
Catalogues of company (click on links to see addresses)

Address

Phone, Fax, e-mail Catalogue numbers
(see table above)
Country of Distribution
Sigma-Aldrich (Sigma-Aldrich Labware Catalogue)
Prizes about 50% higher, but ordering is convenient.
Click link to find 200 countries. Search for "glindemann"
ALDRICH Worldwide,
200 countries,

Lab Logistics Group LLG in UK, Irleand
AJ Cope & Son Ltd 

The Oval, Hackney Road, London E2 9DU, UK Ph: (0044) 0207 729 2405, Fx: (0044) 0207 729 2657, cjc@ajcope.co.uk Lab Logistics Group (LLG) UK, Ireland
AJ Cope & Son Ltd,
on-line shop    Thelabwarehouse.com
The Oval, Hackney Road, London E2 9DU, UK
 
Ph: (0044) 0207 729 2405, Fx: (0044) 0207 729 2657, cjc@ajcope.co.uk
http://www.thelabwarehouse.com/home.html
Lab Logistics Group (LLG) UK, Ireland
Carl Roth in UK, Ireland
ROTEC SCIENTIFIC LTD.
10, Bridgeturn Avenue, Old Wolverton, GB-Milton Keynes MK 12 5QL, UK Ph: 01908 22 33 99,
Fx: 01908 22 30 00, Sales@techmate.co.uk
Carl Roth (ROTH) UK, Ireland
Glass Solutions Ltd.
 
Unit 2 149b Histon Road, Cambridge
CB4 3JD
Ph: (0044) 01223 301929, Fx: (0044)   01223 301623, enquiries@glass-solutions.co.uk Glass Solutions Ltd. UK, Ireland
Lab Logistics Group LLG in Austria
Bartelt ,
Wagner & Munz Austria

click link

click link Lab Logistics Group (LLG) Austria
Carl Roth in Austria
LACTAN GesmbH & Co. KG
Zinzendorfgasse 10-12, A-8011 Graz Ph: 0316/32 36 92-0
Fx:  0316/38 21 60 Lactan.Labor@aon.at
Carl Roth (ROTH) Austria
LABGLASS Pty Ltd

24 Windorah St, Stafford, Brisbane, Queensland, 4053, Australia

Ph: ++61(0)7-3356 8199
Fx ++61(0)7-3356 6722
labglass@gil.com.au

LABGLASS Australia, New Zealand, Oceania
Lab Logistics Group LLG in Belgium
Devos-Francois S.A.

480, rue de Châtelet B- 6010 Charleroi, Belgium

Ph: ++32(0) 71 440870 Fx: ++32(0)71 440890 e-Mail: mail@d-f.be Lab Logistics Group (LLG) Belgium
Carl Roth in Czechia - Ceska
P-LAB A.S. 

Ricanska 10, CZ-10100 Praha 10

Ph: 02/171-380 00, -322 02, Fx: 02/171-311 76, info@p-lab.com Carl Roth (ROTH) Czechia - Ceska
Lab Logistics Group LLG in Denmark
Bie & Berntsen ,
Buch & Holm

click link

click link Lab Logistics Group (LLG) Denmark
Lab Logistics Group LLG in Spain
Serviquimia s.a.
Pere IV 29-35, 5° 1°, E-08018 Barcelona, Spain Ph: 0034 (0)93 3003493, Fx: 0034 (0)93 3003493, serviquimia@serviquimia.com Lab Logistics Group (LLG) Spain - Espagna -
Portugal
Carl Roth in Spain
Carl Roth S.L.
La Jota, 86, E- 08016 Barcelona Ph: 93-3 52 60 61, Fx: 93-3 49 80 23, carl.roth@retemail.es Carl Roth (ROTH) Spain - Espagna
Portugal
Carl Roth in France
Roth-Sochiel S.A.R.L

3, rue de la Chapelle/B.P. 11, F-67630 Lauterbourg, France

Ph: 03 88 94 82 42
Fx: 03 88 54 63 93, sochiel@carlroth.de
Carl Roth (ROTH) France
Lab Logistics Group LLG in France
Sodipro S.A.

42, rue Ambroise Croizat, BP 307, F-38434 Echirolles Cedex, France

Ph: 0033 (0)4 7623 3927, Fx 0033 (0)4 7623 2412, sodipro.38@wanadoo.fr Lab Logistics Group (LLG) France
Fisher Scientific Germany

Im Heiligen Feld 17 58239 Schwerte

Ph++49 (0)2304 / 932-800
Fx++49(0)2304 / 932-957

Fisher Scientific Germany Germany, Austria, Switzerland
VWR in Germany

John Deere Str. 5,
D-76646 Bruchsal, Germany

Ph++49 (0)7251/717-0
Fx++49 (0)7251/717-182

Merck Eurolab (VWR) Germany, Austria, Switzerland
Lab Logistics Group LLG  Germany

Postfach 1416
D-37004 Göttingen, Germany

Ph++49(0)2225-948690,
Fx ++49(0)2225-948691

Lab Logistics Group (LLG) Germany
LR. Vetter Laborbedarf e.K. Herrenberger Str. 5, D-72119 Ammerbuch, Germany Ph++49(0)7073/6936, Fx++49(0)7073/2740 Vetter Germany
Carl Roth GmbH, Germany

Schoemperlenstr. 3, D-76185 Karlsruhe, Germany

Ph++49 (0)721/5606-0,
Fx++49 (0)721/5606149

Carl Roth (ROTH) Germany
Lab Logistics Group LLG in Italy EXACTA + OPTECH labcenter s.p.a. click link click link Lab Logistics Group (LLG) Italy
Lab Logistics Group LLG in the Netherlands
Boom B.V.
P.O. Box 37 NL-7940 AA Meppel Rabroekenweg 20 NL- 7942 JE Meppel  Ph: ++31(0)522 268700 Fx: ++31 (0)522 260779 boombv@boomlab.nl Lab Logistics Group (LLG) Netherlands
LABGLASS Pty Ltd

24 Windorah St, Stafford, Brisbane, Queensland, 4053, Australia

Ph: ++61(0)7-3356 8199
Fx ++61(0)7-3356 6722

LABGLASS New Zealand, Oceania
Lab Logistics in Norway INSTRUMENT-TEKNIKK A/S BIOTEST (Member of the Bie & Berntsen-Group0 Grini Naeringspark 1/PB 14 N-1332 Oesteraas (Oslo) Ph: ++47 (0)671 49303 Fx: ++47 (0)671 49302
firmapost@instrument-teknikk.no
Lab Logistics Group (LLG) Norway
Carl Roth in Poland
Linegal Chemicals Sp.z o.o.
ul. Kasprzaka 44/52, PL-01-224 Warszawa Ph: 022/632-32 21 w.-33 74,-31 92,-32 91,
Fx: 022/631-72 81
Carl Roth (ROTH) Poland - Polska
Lab Logistics in Sweden
Bie & Berntsen,
Buch & Holm
click link click link Lab Logistics Group (LLG) Sweden
AMSI-Glas AG

Geismet 11, CH-4317 Wegenstetten AG, Switzerland

Ph ++41-(0)61-8739093, Fx ++41-(0)61-8739094 AMSI-Glas AG Switzerland
KIMBLE-KONTES 1022 Spruce Street, Vineland, NJ 08360 Ph ++1-609-692-8500, Fx ++1-609-692-3242 Kimble-Kontes USA/Canada/Mexico
VWR USA 1310 Goshen Parkway
West Chester, PA 19380, USA
Ph 1-800-932-5000, Phone: (610) 431-1700
Fax: (610)431-9174
VWR USA USA/Canada/Mexico
Fisher-Scientific USA Fisher Scientific Worldwide, Export Division, 50 Fadem Road, Springfield, NJ 07081-3193, USA

Phone: 1-973-467-6511,
Fax: 1-973-376-1546

Fisher-Scientific USA USA/Canada/Mexico
ALDRICH (since  September 2002)
Prizes up to 50% higher, but ordering is convenient.
Click link to find 200 countries
ALDRICH Worldwide,
200 countries

 

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Delivery:
For taper joint sizes from 7 to 70 mm diameter.

1 unit of delivery = 50 sealing rings stored on a tube or cone matching the diameter of the male joint part, in a labeled bag including information in several languages:

                  
                                   50 rings on a storage tube
Kartusche Farbphoto mit Glas und Ring und Pfeil.jpg (12270 bytes) Foto:
50 PTFE rings
on a plastic storage tube
fitting joint 29 mm.

Retail-Prices in Europe: 1 unit of delivery (50 rings) about 25...35 EURO (ask your trader).

 

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Instruction where to use and how to use GLINDEMANN®-sealing rings
Application: Laboratory work with glass equipment and containers often demands hermetic and clean sealing of conical joints and stoppers. Joint grease is not solvent resistant and not clean. The known PTFE-joint sleeves and stoppers are expensive and not very tight. Therefore, a fine PTFE-ring seal made off PTFE (known as Teflon) on ground tapered glass joints has been developed.
Use for hermetic sealing of equipment and containers without grease. Pressure- and high-vacuum tight (gas leak rate below 10-6mBar l /sec). Chemically resistant and tight (solvent leak rate below 0.2 mg/day). Temperature resistant (-200 to +300oC). No irreversible jamming of the joint. Useable with all joint clamps. Reusable. Available for all joint calibres: NS 7, 10, 12, 14, 19, 24, 29, 34, 45, 50, 60, 70.



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Procedure:
Slip a sealing ring onto the male part of the joint.
The ring adheres by elastic tension. One ring is normally enough. Two rings with about 3 mm distance. Make sure that the ring is not twisted.

Delivery: 50 sealing rings on a tube, matching the diameter of the male joint part.

The sealing ring looks on good joints "tightly" like grease.

Gently press the glass parts together. The ring must look transparently "tight" all around. Do not break the joint by overstressing. For less smooth glass joints a miniscale amount of grease should be used. The parts of the joint can also be rotated and rubbed to produce microscopic PTFE-filings which smooth the glass.

The sealing ring becoming "visibly" tight
On the left: Ring before pressing the 2 joint parts together

 

Centre: Ring after pressing - transparently like grease. Under pressure the PTFE, although free of grease, flows like grease into the uneven surface of the ground joint

On the right: Compared to a greased joint, equally transparent. But grease is not solvent resistant and not very clean.


Disconnect the joint by moving one part of the joint back and forth (do not pull).
With 2 rings extra motion.

 

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Frequently asked questions and Know How on PTFE sealing rings for Taper Joints

QUESTION: Ordering. Where can I order these PTFE sealing rings? ANSWER: Search the list of traders at this homepage. If your home trader is not on the list ask him to manage to buy sealing rings from one of the listed traders for you.

QUESTION: Sizes. Are sealing rings available for all joint sizes? ANSWER: Yes. Rings are available for 5...70 mm taper diameter.

QUESTION: What is the price of these PTFE sealing rings?
ANSWER: The price is in Europe about 25 Euro per unit of delivery (50 rings). So one ring is about 0,50 Euro.

QUESTION: How does the PTFE ring seal work?
ANSWER: The plastic PTFE (known as Teflon) of the sealing ring acts similar to joint grease. But PTFE is much more clean and chemicly inert than joint grease. The PTFE flows under  high pressure slowly like grease or wax into the uneven spots of the ground glass surface. By this cold flow the free leakage volume between the 2 joint parts is filled and sealed by PTFE. PTFE is in fact much harder than grease or wax. To make PTFE flowing like grease it must be under a very high pressure. This pressure is produced by pressing the 2 glass joint parts together. But the force to produce this pressure is applied to the PTFE and the glass as well. This force can break the female part of the glass joint by tensile stress. But the glass is of course not allowed to break ever. Therefore, the PTFE ring is shaped to contact the surface of the ground joint only at a very small area (just the area of the 0,6 mm wide ring). If you force the 2 glass joint part together they contact each other only via the small PTFE ring. This relatively small force results therefore in a comparatively large deformation pressure on the PTFE. With this theory on PTFE ring seals in mind you can use the following rules to use these rings more efficient: Any factor which makes the PTFE more soft makes the seal better (high temperature, presence of traces of plasticizers, solvents, water, grease). Any factor which makes the ground glass surface more smooth makes the seal better (polishing of the glass surface). Any factors which gives the PTFE more time to flow makes the seal better (usually the final sealing is better a few hours after pressing the joint together).

QUESTION: I have doubts that PTFE can seal a glass joint properly. I used PTFE-sleeves and found they have no sealing properties compared to a bare glass joint.
ANSWER: The common PTFE sleeves which do not have sealing ribs have in fact no sealing effect because they do not work like PTFE rings. PTFE sleeves cover the whole joint. Therefore, the pressure on sleeves is too low to make the PTFE flowing like grease.

QUESTION: Sealing Containers. Can I use the PTFE sealing rings to seal containers with glass taper stoppers? (Reagent tubes, flasks, erlenmeyer flasks, bottles)
ANSWER: Definitely, this works great. You fill find, that the PTFE sealing ring will make the glass stopper fixed in the container. Therefore, a slight overpressure in the bottle will not push out the glass stopper. To loosen the glass stopper, do not pull the joint parts apart because this needs too much strength. Instead, move the stopper to and from several times or rotate one joint part.

QUESTION: I can not remove the stopper with a sealing ring from the joint or bottle. Why are the glass joint parts with a sealing ring stuck if I try to pull them apart?
ANSWER: Do not pull the joint parts apart because this needs too much strength. Instead, move the stopper to and from several times or rotate one joint part.

QUESTION: Can I use the ring more than one time?
ANSWER: Yes. The ring can be removed from one joint and can be transfered to another joint. But scratches and dirt can make it less tight over the time.

QUESTION: How can I remove the PTFE sealing ring from the glass joint?
ANSWER: Just slip it off. The PTFE rings adheres to the male glass joint just by elastic tension, which prevents the PTFE ring from falling of the male glass joint.

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QUESTION: Extra tight seal. I used a PTFE ring seal and found the sealing not proper enough.
ANSWER:
Inspect the seal if it looks transparently "tight" all around the joint. If there are "bad" looking spots (one millimeter is enough to cause leakage) then the ring is probably scratched or dented.
Some times the surface of the ground joint is simply to rough to fit the PTFE ring seal.
There are different possibilities to smooth out the roughness of ground jointed glass ware.
The joint with a PTFE ring seal can be rotated and rubbed to produce microscopic PTFE-particles which smooth the glass at the PTFE-contact zone forever. This zone of the joint looks like greased but it is in fact a layer of small PTFE particles which fill out the uneveness of the ground glass. To make the smooth contact zone broader move the PTFE ring on the joint and rotate the joint parts again. Remove larger visible PTFE-fibres after this procedure. The PTFE-ring used for rubbing has to be sacrificed often because it looses larger PTFE-particles which make the ring uneven.

wpe5.jpg (14027 bytes) Foto:
Extra tight seal.
Smooth a 2 mm zone of the male glass joint with PTFE filings from a ring by rubbing. Sacrifice this ring used for rubbing. Slip a new PTFE Ring onto the smoothed zone. This extra smoothing will result in an almost hermetic extra tight seal.
But you can of course use PTFE sealing rings without this procedure, for most purposes.

Another possibility is to soften the PTFE sealing ring.  This can be performed by applying a micro scale amount of grease or solvent or water.Do not clean your jointed glass in Potassium Hydroxide solution which makes ground glass even more rough. You can also ask your glass blower for slightly polishing the joints. A simple home made fire polishing procedure is to direct a very hot welding flame (more than 2000oC) for a few seconds (do not deform the joint) directly around the grounded glass surface.
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QUESTION: Extra clean work: How can I extra clean the PTFE ring for ultra clean work (biochemical, pharmaceutical, analytical, organometal work) ?
ANSWER: You can either bake the ring or you can extract contamination with solvents.
Baking: The PTFE ring can be baked at 300 oC in an oven. But do NOT put the plastic storage tube at heat over 100 oC! Slip the PTFE ring on a male glass taper stopper to prevent it from shrinking .
Solvent extraction: You can bathe, purge or rinse the PTFE rings with any useful solvent (PTFE takes any organic solvent). You can also put many PTFE sealing rings alltogether in a Soxhlet Extractor and rinse them with the solvent, which has a boiling temperature below 70 oC (at higher temperature, the rings will start to shrink).
Take care, that this cleaning (baking or solvent rinsing) will make the PTFE less soft and reduce the sealing power slightly. If you want to soften the PTFE ring again, you can add a micro amount of any greasy, oily or slippery chemical  which does not harm your laboratory work.

QUESTION: How can I prevent that the sealing ring teared up and fell off   the joint after baking/heating over 200 oC?
ANSWER: Slip the ring before heating on the thinner part of the taper joint.

QUESTION: I took the ring off the joint and it contracted to be too small to install it again on a taper joint.
ANSWER: You can stretch the ring  to fit again the joint. Stretch the ring with a storage cone which you bought together with the rings from your trader. You can also use two fingers, sticks, nails etc.
wpe6.jpg (8779 bytes)Foto:

Sealing ring contracts (shrinks)
if removed from the joint.

 





wpe3.jpg (12584 bytes)

QUESTION: The sealing ring became to large in diameter and fell off the joint.
ANSWER: The diameter of the ring can be decreased by use of high temperature of 100...300 oC (oven, lighter, Bunsen burner).

 

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User opinions about GLINDEMANN rings

1. Test report of GLINDEMANN-PTFE-sealing rings for ground tapered joints
from: Dr. Andreas Bolte, Group Prof. Dr. Borislav Bogdanivic, Max-Planck-Institute of Coal-Research, Germany
Dear Dr. Glindemann:
Our inorganic and organometallic laboratory research needs often absolute clean and tight sealing of tapered joints on glass equipment.
Your PTFE-sealing rings proved to be a success while:
long term sealing of high vacuum equipment,
long term sealing of inert equipment until 200oC,
sealing of equipment and containers for synthesis and storage of dangerous (inflammable in air), oxygen sensitive and moisture sensitive chemicals,
sealing of equipment where contamination of reaction mixtures by joint grease has to be avoided.
Our group has gone over to use Glindemann-sealing rings instead of joint grease or PTFE-sleeves because of the amazing sealing properties and the advantages of working with greaseless joints.
(some extended information in the German version is not translated here)
We consider your PTFE-sealing rings as the present most advantageous way to work with greaseless and tight joints.
(signed by Andreas Bolte)

2. Test report of GLINDEMANN-PTFE-sealing rings for ground tapered joints
from: Professor Michael D. Fryzuk, Department of Chemistry, University of British Columbia, Canada
Dear Dr. Glindemann:
Thank you for the sample of your amazing o-ring seals. We have used Teflon sleeves in the past for certain situations but we have discontinued this practice because they are too expensive and not particularly effective. We have tested your o-ring seals using an extremely air-sensitive solution of {Co2TiCl}2ZnCl2 in toluene. This material is our indicator for O2 in our inert-atmosphere glove boxes since it goes from deep blue green to bright orange in the presence of 5 ppm of O2. A tube with 3 mL of this deep blue green solution was sealed with a stopper that had one of your seals and no grease inside an inert atmospheres glove box; the tube was then removed to the outside and inverted so that the solution was on top of the stopper. The colour could be seen to penetrate to the o-ring seal and no further. And amazingly, the solution remained blue green for many days. This tells me convincingly that this seal is airtight and robust. I would buy such a product because it is ideal for our research on air- and moisture-sensitive organometallic complex compounds.
Sincerely,
M. D. Fryzuk
for <dglinde@chem.ubc.ca>; Tue, 10 Mar 1998 08:47:40 -0800

3.
Test report of GLINDEMANN-PTFE-sealing rings.
from: Fan Ouyang, Beijing University of Aeronautics and Astronautics, April 24, 2003
My name is Fan Ouyang. I am a senior undergraduate at Beijing University of Aeronautics and Astronautics. I am now engaging in a new compound synthesis.
In our synthetic chain, there was a key link that should be reacted at high temperature (>110
) and high pressure (>8 Bar) for 12 hours. To realize the condition, we designed thick-wall glass tube to bear the high pressure, but in practice, we found the standard conical joints could not meet our hermetic requirement that a low-boiling-point reagent (5 ml) leaked completely in less than one hour.
Fortunately, in a journal, we saw the Glindemann-Sealing Ring. These sealing rings were designed for standarded conical joints that they are available for all joint calibers: NS 7,10,12,14,19,24,29,34,45,50,60,70.
We used the 19-sized sealing-ring. As it was described at the references, the sealing ring was very effective. Not only could it be used under high temperature, but also after 12 hours reaction with the high air pressure, the low-boiling-point reagent leakage rate was less than 10% (0.5ml/5ml).
Thanks to the Glindemann sealing-ring, our experiment finally got a complete success.
So I am glad to introduce this effective and convenient ring to my dear colleagues in China. Besides their excellent hermetic and vast application conditions, they can conveniently change a common joint into a hermetic joint so that it can save the investment on specialized equipment.
我叫欧阳凡,现在是北京航空航天大学大四学生。我现在正在合成一种新型化合物。在我们的合成路线中,有一个非常关键的步骤,需要在高温(>110)高压(>8个大气压)条件下反应12小时。 为达到这一目的,我们设计了厚壁的玻璃仪器来承受高压, 但是在实际操作中,我们发现标准磨口在我们的实验条件下不能达到要求的密封程度,一种低沸点的反应物(5ml)会在不到一小时完全泄漏。很幸运,在一本杂志上,我们发现了Glindemann密封环的广告。这种密封环是专门为标准磨口设计,型号有71012141924293445506070,可以应用于各种磨口。抱着试一试的心态,我们使用了19口的密封环。正如其产品说明中介绍的一样,这种密封环非常有效。其不但可以在高温下使用,而且在> 8个大气压的气压下反应十二小时后, 低沸点的反应物泄漏不超过10%0.5ml/5ml)。在这种密封环的帮助下,我们的实验最终取得了成功。 因此我很乐意向大家推荐这种密封环。 除了其优异的密封性能和广泛的使用条件,其最大的优点就是可以方便的使普通标准磨口达到很好的密封性,可以节约专门的密封设备的投资。这尤其适合中国的国情。

4. Test report of GLINDEMANN-PTFE-sealing rings.
from: Dr. Konstantin Chernichenko, University of Helsinki, Department of Chemistry, August 3, 2016
Dear Dr. GLINDEMANN,
...I would like to express my gratitude to you for invention and commercialization of the rings. I hardly imagine my lab work without Glindemann rings, I use them not only for gas-tight reaction like hydrogenations, but for all the synthetic work I do and encourage students and colleagues to do same. In fact, I haven't been using any grease since I found out about the rings from a colleague some 7 years ago.

5. Test report of GLINDEMANN-PTFE-sealing rings.
from: an unknown user "mrj" at http://blogs.sciencemag.org/pipeline/archives/2008/05/30/ah_glassware
"...21. mrj on May 31, 2008 10:53 PM writes... I am surprised to find nobody mentioning Glindemann sealing rings (www.glindemann.net). They are just so superior to grease or teflon sleeves, there is no comparison. I don't use anything else for high vacuum work ( ."

 

The Suppliers Guide of the American Scientific Glassblowers Society
is listing
GLINDEMANN® (PTFE Sealing Rings for conical glass joints) and
www.glindemann.net.
Copied from: http://www.asgs-glass.org/asgs/pages/adlinks_start.htm
Welcome to the ASGS Suppliers Guide
The following are links to ASGS advertiser web sites. We encourage you to consider these companies when making purchasing decisions for your glass needs. Please let these companies know that you saw their link at the ASGS web site.
Vacuum Supplies: http://www.asgs-glass.org/asgs/pages/adlinks_s-z.htm

Glass Components (Stopcocks, Joints, etc.): http://www.asgs-glass.org/asgs/pages/adlinks_g-k.htm
Health and Safety Equipment: http://www.asgs-glass.org/asgs/pages/adlinks_g-k.htm
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Links on laboratory glass ware in the internet and to www.glindemann.net:
(If You would like your scientific glass web site mentioned on this page just e-mail me at dglinde@aol.com)

The British Society of Scientific Glassblowers listing www.glindemann.net as a supplier
The American Scientific Glassblowers Society listing www.glindemann.net as a supplier

Glassblowing Workshop of Colin F. M. Smith  
WHY YOU SHOULD NOT USE SILICON GREASE ON YOUR GLASSWARE

The Glassware Gallery, Glassware, Joints (by Rob Toreki)
Kimble-Kontes. Great sites to gather additional information. Glindemann Seals
LabOnline Australia. Feature Story - Sealing Your Ground Joints. Glindemann sealing rings.
Glassblowing workshop of Gary Coyne - one of the finest how-to-use-joint-grease advices (3 types of joint greases versus Glindemann PTFE Sealing Rings)
      (in case this link is broken, download here Gary Coyne's joint-grease advices)
G.M. Associates, Inc, one of the largest Manufacturers of Quartz Glass Taper Joints (Quartz Glass Conical Joints),

Scientific Glassblowing Societies
American Scientific Glassblowers Society
Belgische en Nederlandse Vereniging voor Glastechniek
British Society of Scientific Glassblowers
German Scientific Glassblowers
Leidse Instrumentmakers School
Scientific Glassblowers Association of Australia and New Zealand 
Scottish Glass Society
Vereinigung Österreichischer Glasbläser

Other Glass Links
http://groups.yahoo.com/group/Scientific_Glassblowers/
Scientific Glassblowing Basics (East Carolina University)
Glassblowing Workshop of António Morais, University of Aveiro, PORTUGAL
www.glassline.net/links/links.html
www.glassonline.com/
www.glassartists.org