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4280 Marie Court
Fremont, CA, 94536
United States


At USA Pen Company, we craft pens and pencils in a small utility workshop of a house in Elk River, Minnesota.  We use exotic wood and acrylic to hand make our pens. Our selection over the past few months has evolved into an assortment of contemporary designs... Come take a look at our collection and choose your favorite to either gift to your loved one, or keep all for yourself! 

All our pens and pencils are handmade in the United States of America (USA).

Welcome to the art of pen and pencil making at USA Pen Company. 

Would you rather have synthetic plastic or the feel of rich natural wood in your hand? We make our pens with carefully selected exotic wood from different parts of the world! 

Do visit our Gallery and Lookbook. If you like any pen currently not available in our "BUY NOW!" page, email us the details and we will specially handcraft and ship it to you within 14 days of your order. 

We look forward to serving your needs. Thanks!

Centrifuge Guide

Service AI support guide for centrifuge questions. Please feel free to email us at

Filtering by Category: Centrifuges

Why do centrifuge tubes leak?

Service AI

Most leaks are due to improper handling or sealing. Always refer to the Rotors and Tubes manuals before attempting to use the rotor.

 1.     OptiSeal™ : Make sure the neck area is dry and tubes are correctly filled.

 2.     Quick-Seal™ : Fill to the base of the neck leaving a small (approx. ¼" diameter) air bubble and seal with the proper Beckman Coulter heat sealer and seal former. For best results, follow the Quick-Seal™ user's booklet directions.

 3.     Open top tubes: Thinwall tubes must be capped and filled for use in fixed angled rotors (torque the cap to 120 inch-pounds). In swinging bucket rotors the fill level is 2 - 3mm from the top. Thickwall tubes (without caps) in fixed angled rotors need to be filled between half to three-quarters full. In swinging bucket rotors fill to within 2 - 3mm from top.

4.     Bottles: Always ensure all sealing surfaces and O-rings are dry. Wet O-rings can act as a pathway for fluids, causing a leak. Be sure all O-rings are present, in good condition, and are dry.

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What RPM can one use with a Beckman Coulter rotor to obtain the desired "g" force ?

Service AI

The RPM/RCF information is included in each rotor operator's manual. You can also use the G-Calculations program found at this Beckman Coulter website link to obtain this information. Also, many Beckman Coulter centrifuge models can be programmed using RCF ("g") or RPM so that this calculation is not necessary when using these models.

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How to get a stuck tube out of the centrifuge rotor...

Service AI

To remove a tube when using swinging buckets, remove any tube cap or closure and tube contents. Always invert the buckets when putting them into an autoclave. Autoclave the rotor at 250 degrees Fahrenheit, for 15 minutes at fast exhaust. The tubes or bottles should loosen or soften enough to slide out.

If it is a fixed angle rotor - uncap, vent, and empty the tube; invert the rotor over a clean wash basin, if necessary, with the lid off, and put the rotor into an autoclave. Use the same autoclave cycle as with swinging bucket rotors.

Important Note: You should NEVER try to remove a tube with a sharp object. If a spacer or cap is stuck, DO NOT autoclave; try applying dry ice to the cap or spacer.

Service AI support guide for centrifuge questions. Please feel free to email us at

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