MAS Phenolic Micro Balloons, 1 Qt, 25-007

  • $27.50
  • Save $6.45

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Product Overview:

MAS Phenolic Mirco Balloons are used to thicken epoxies and make a low-density, light-weight fairing material that can easily be shaped, sanded and painted.

Ideal for shaping, filling cracks, fixing chips and dings and resurfacing.

MAS Micro Balloons are made of hollow microscopic phenolic spheres and have a purple-brown color. Micro Balloons offer a great strength to weight ratio.

When used in conjunction with Colloidal Silica it can be pulled or drawn to a feather edge that is easily sandable when cured. Add an equal amount of Colloidal Silica by volume to the mixed epoxy and then thicken the rest of the way with Phenolic Micro Balloons.

Features and Benefits:

  • Used to make low-density and light-weight material that can easily be faired, filled, sanded and painted
  • Ideal for shaping, filling cracks, fixing chips and dings and resurfacing
  • Great strength to weight ratio
  • Great when used in combination with other fillers to make smoother and ease spreading

How To Make Professional Fillets and Fairings:

Starting Formula:

Trowelable Fairing:

  • 1 Part MAS Resin/Hardener mix using "Medium" hardener (or 50/50 MAS "Slow/Fast" Hardener)
  • 1 Part Cab-O-Sil
  • 3 Parts Phenolic Micro-Balloons 
  • Reduce the amount of Micro-Balloons if a looser mix is required


  • 1 Part MAS Resin/Hardener mix using "Medium" hardener (or 50/50 MAS "Slow/Fast" Hardener)
  • 1 Part Colloidal Silica
  • 2-3 Parts Wood Flour


It is important to mix epoxy and hardener thoroughly before adding thickener.

Often two fillers used in conjunction are more effective than any single filler used alone; this can be attributed to the synergistic effects found when two different particle sizes are blended together.

When filling gaps or making a fillet (pronounced "fill-its") add sufficient wood flour to make a peanut butter consistency. 

Colloidal Silica (AKA Cab-O-Sil) and other white fillers may be added to make the wood flour paste match the color of the plywood exactly. Adding some Phenolic Micro Balloons or Colloidal Silica (no more than 30 percent by volume) has the added benefit of making wood flour fillets smoother and easier to spread.

When using epoxy as an adhesive (i.e., bonding wood to wood), add enough silica powder to the resin-hardener mix to bring it to the consistency of mayonnaise or jam.

When simply coating, sealing or saturating wood with epoxy, do not add thickening powders.

Data Sheets:

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