Field Notes

DOWSIL 795 — ASTM C1184 Sealant, Case of 16
The one sealant on this site that carries ASTM C1184 and C920 Class 50 by name. What that means on a submittal, and when nothing else will do. Read more...
Where to Buy Glazing Supplies in the New York Metro
Six ways to get sealant, backer rod and shims in the NY metro, what each is good at, and where each one costs you a morning. Written by one of them. Read more...
Sealing in Cold Weather: What Actually Goes Wrong Below 40F
New York seals through the winter whatever the data sheet says. What cold does to cure, adhesion and joint width, and how to work with it. Read more...
Self-Drilling Screws for Storefront: Point Size, Length and Why 410 Stainless
The drill point is sized to the metal, not to the screw. Get it wrong and the screw work-hardens the hole and snaps. Point, length and material. Read more...
12:1 or 18:1? Choosing a Sausage Gun for Structural Silicone
The ratio is leverage, and thicker sealant needs more of it. What the number means, which ratio suits which grade, and why sausages beat cartridges. Read more...
Why Sealant Joints Fail: Five Causes, Four of Them Avoidable
Most failed beads did not fail because the sealant was bad. Three-sided adhesion, wrong joint shape, a dirty substrate, or the wrong temperature. Read more...
Horseshoe or U Shim? Measure the Anchor, Not the Shim
The two shim lines look alike and are not interchangeable. The bolt hole decides it: 7/8 inch for horseshoe, 1/2 inch for U. Which your job takes. Read more...
How Much Sealant Does a Joint Actually Use?
Linear feet per sausage for every common joint size, the arithmetic behind it, and the two things that push real site usage above the table. Read more...
Horseshoe Shim Colours: There Is No Industry Standard, and That Is the Problem
Blue is 1/16 inch here and 1/8 somewhere else. There is no industry standard for shim colour. Our chart, and how to check a box you did not buy. Read more...
Neutral Cure or Acetoxy? On Aluminium There Is Only One Answer
Acetoxy silicone gives off acetic acid as it cures and attacks coated aluminium. What actually happens at the bond line, and what to use instead. Read more...
Structural or Weatherproofing Silicone? They Are Not Interchangeable
One holds the glass on the building, the other keeps water out. How to tell them apart, and what to do when the spec calls for ASTM by name. Read more...
What Size Backer Rod Do You Need? A Chart by Joint Width
Measure the joint, then take the rod one size up. A chart of rod diameter for every common joint width, and why a loose rod is worse than none. Read more...