Sealants

Archive of Older Topics Archive - Product Discussions #6
1

Our office master has this listing:

“Silicone Sealant: ASTM C920, Grade NS, Class 25 minimum; Uses NT, A, G, M, O; single component, neutral curing, non-sagging, non-staining, fungus resistant, non-bleeding.”

Can one type of sealant cover all of these requirements?

Thanks for all who contribute to these forums. Such a great resource

2

Yes
B. Silicone General Purpose (Designation S-GP): ASTM C920, Type S, Grade NS.

  1. Class: Joint movement range without cohesive/adhesive failure: Plus 50 percent to minus 50 percent of joint width.
  2. Uses: NT, M, G, A, and O.
  3. Low to medium modulus, single component, neutral curing, nonstaining, nonbleeding.
  4. Acceptable Products:
    Dow Corning Corporation; 790, or 795.
    GE Silicones; SilPruf LM SCS2700.
    Pecora Corporation; 890 or 895.
    Sika; Sikasil WS-290 and WS-295.
    Tremco; Spectrum 1 or 3.
3

Dewayne - one sealant, perhaps, however priming becomes necessary for different substrates, based on project specific preconstruction test results with your substrates. Avoiding primers is a positive thing in my opinion, and perhaps a reason for so many different sealants.

Wayne has listed a collection of high quality silicones I’ve seen and used numerous times for general applications, however for non-bleed/low stain potential applications (note - preconstruction testing required for manufacturer to standby their “no-stain” claim):

Dow Corning 756 SMS (“surface modified sealant”)
GE/Momentive Silpruf NB (“non-bleeding”)

General purpose silicones only capable of +/-25% movement…this is low performing (on par with a polyturethane) and would require doubling the width of a caulk joint to handle the same amount of movement relative to a +/-50% sealant. For a 1/2" of movement, do you want a 1" or 2" sealant joint?

4

Thank you gentlemen