Thixotropic Silica

4 star rating

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  • Item
  • Description
  • Price
  • Qty
  • 23-A
  • 23-A
    1/2 Gallon (6 oz)
  • $17.95
  • 23-C
  • 23-C
    Carton (7 lbs)
  • $199.95
  • 23-E
  • 23-E
    Carton (16 lbs)
  • $389.95
  • 23-D
  • 23-D
    Bag (30 lbs)
  • $749.95


Prevent Sags on Vertical Surfaces

A white, free-flowing powder, Thixotropic Silica is a thickening agent primarily added to resin to prevent run-off and sags on vertical surfaces.

  • Use with an epoxy to produce extremely hard, solid parts, perfect for structural bonding, filling, and filleting.
  • Use in conjunction with chopped glass fiber for added strength for parts.
  • Silica-filled resin can be difficult to sand. Consider using #22 Glass Microspheres for areas that require sanding.

This filler is compatible with epoxy, polyester, and vinyl ester resin systems. Add filler after adding catalyst to resin.

Mix ratio is 1:2 (filler to resin by volume) for general use, 1:3 (filler to resin by volume) to reduce runs/sagging.


Fillers, when ordered alone, will typically ship in a small or medium box. Where possible, we will combine ordered items to reduce the number of boxes shipped.


Thixotropic Silica Silica is available in a variety of sizes: One 1/2 gallon (#23-A) One carton (#23-B) One bag (#23-C)


4 star rating

Excellent Bonding Filler

Feb 9, 2017  |  By Klaus Composites

We use it for general bonding of composite to composite and aluminum to composite. Very smooth and easy to mix to any viscosity ranging from catsup to peanut butter. The exceptionally smooth nature of the silica powder results in a stronger and less porous bonding filler than we've seen from West System colloidal silica or other silica fillers.

Test and plan for your vertical installation

Jan 7, 2017  |  By Todd Duffett

When using the Thixotropic silica to bond a horizontal bulkhead to nearly vertical sides of my sailboat hull interior we had considerable difficulty due to the low viscosity of the mix at the recommended ratio of 3:1. We did not prepare a test batch before hand and therefore did not plan to use clay or some other form of a dam to control the slumping of the mix. Ended up using masking tape on the underside surface but it was quite a mess as a result. Perhaps the ratio needs to be reviewed or additional thickening agents should have been added for a vertical installation.
Owner Response: Thanks for the review! We are sorry that the product did not perform to your expectations. The mix ratio can be customized to your application, and can vary due to differences in climate and resin used. We recommend on the product data sheet a General Use ratio of 1:2, and a Vertical/Overhead ratio of 1:3. Thanks to your review, we will also better clarify this on the product label.

Product Q&A