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These K-20 series bubbles are actually hollow glass spheres. Because this high-quality glass is very crush resistant, the foam is much stronger, stiffer and water-resistant than any foam made by chemical foaming. These foams displace 4-6 times their weight in most resins and improve the handling characteristics of the base resin. They have a low bulk density and are nontoxic. Mix resin and hardener as directed, then fold in the glass bubbles. Upon cure, a strong, low-density product results which is easy to sand and file. May be shaped to form compound angles and curves.

The term "micro" was applied to the mixture of microspheres and epoxy early in the development of composite structures. Although microspheres have been replaced by glass bubbles the word "micro" is still commonly used to reference the mixture. "Micro is used to fill voids and low areas, to glue foam blocks together and as a bond between foams and glass cloth. Micro is used in three consistencies - (1) a "slurry" which is a one-to-one by volume mix of epoxy and glass bubbles, (2) "wet micro" which is about two to four parts glass bubbles by volume to one part epoxy, and (3) "dry micro" which is a mix of epoxy with enough glass bubbles to obtain a paste which will not sag or run (about five parts to one by volume). In all instances, glass bubbles are added to completely mixed epoxy resin and hardener. Wet micro is used to join foam blocks and is much thicker than slurry (it has the consistency of honey) but can be brushed. Dry micro is used to fill low spots and voids and is mixed so that it is a dry paste and will not sag. Apply with a putty knife. Never use micro between glass layers.

CAUTION - When mixing epoxy and glass bubbles, wear a dust mask and keep your face away from the balloons that may float up into the air. Although glass balloons are inert, they can lodge in your eyes or in your lungs and cause problems. Handle with care.


Exactly what I was looking for. Great packaging! Arrived quickly and no damage

Michael G
September 4, 2020

Always clean and dry. Same great product that Aircraft Spruce always offers.

Dale M
July 30, 2020

Received in good condition. Micro balloons for Hysol work on my Kitfox.

Bill M
April 4, 2020

This is a superb low density epoxy filler (ArtResin - strong bonding, syrup initial viscosity) at a low price/volume (about 30% void space fill for a thick paste). The spherical filler allows high solids loading for a given final viscosity. ALWAYS PRE-MIX THE EPOXY! Add filler, mix carefully (dusting), pause to allow the epoxy to wet, then mix some more (dilatant fluid). Patience.

Al S
January 28, 2020

Good source of micro spheres at fair price with fast shipping.

October 22, 2019

Liked this product and have always used glass bubbles with fiberglass and it is a great product

Modesto V
October 15, 2019

I use this product mostly as a lightweight filler. I also appreciate that this is shipped double-bagged.

Chris D
July 15, 2019

Using EA9309NA with the beads to create a smooth filler and matt application for a repair with Vac bagging, works great.

April 25, 2019

Upon the recommendation of other guys in the classic car hobby, I used these beads to make a heat and sound insulating paint for the floor of my old Dodge. It mixes very well and goes on nicely. I wont know how well is works for a while yet, but I know from the testimony of others, that it does indeed make a huge difference. Thank you.

April 14, 2019

Glass Bubbles make your epoxy light and stiff to hold shape (Micro). For structural uses Flox is much stronger.

Buck S
March 9, 2019


Q: What is the diameter (size) of these 3M glass bubbles?

Please see the Tech Data Sheet located in the "Documents" tab of this web page. Reference product K20. It has all available technical information including particle size.

Q: How many pounds are in a gallon of 3M glass bubbles?

1 pound of material is in a gallon bag.

Q: When sanding a cured mixture, do I need to be as carefull as in when mixing the bubbles into the resin-is it neccesary to wear a mask?

It is always good to wear breathing protection when sanding any material.

Q: What mixing ratio would I use to insulate the footwells of my car and can I use Rustoleum solvent based paint instead of latex?

We do not have any data for this product for use as you decribe. This has been used as a filler for laminating epoxies to make a slurry for finishing the surface of composites parts. It is commonly used when mixed with an epoxy to a toothpaste like consistency. Once fully cured, you can use the primer and top coat paint of your choice.

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