Silicone Caulk can be a Window Cleaners nightmare! The reason for this is that as silicone caulk cures it forms a covalent bond with itself (it crosslinks), and to the 'free' oxygen atoms at the surface of the glass. So in other words it bonds to itself and the window. The common solvents out there that won't kill a mouse at fifty feet, will at best only soften cured caulk. They will not 'eat it up'. My aproach to this was to find the most effective but environmentally friendly solvent, for softening cured silicone caulk. Then to find the best microcrystalline optical grade polishing powder to break it up and remove it completely from the window. The powder I chose would also need to blend well with the solvent chosen. This post will explain how I went about developing The Slayer.
In looking for the best solvent I knew that I needed one that wasn't stinky. At times we must use it inside. Also it must have a slow evaporation rate. Even in the hot sun. Because we need time to scrub a little. It must also be water miscable so we can remove it easily from the window with our cleaning solution. And it must be extremely powerful at softening fully cured silicone caulk.
Silicone caulk will not bond to plexi and lexan. It peals off with extreme ease when fully cured. It comes off lexan even easier than plexi. So I picked up some new one by one foot squares of plexi and lexan from the local glass shop. Then I created several long thin strips of fully cured clear silicone caulk from a tube. Which I also got from the glass shop. These strips pealed off the lexan leaving a very flat and smooth underside. So they would temporarily cling to vertical glass for experimental purposes. They held on very well, but came right off when I was done. Then I just threw them away.
Before I put them up for testing I suspended each in a separate glass cup with a different organic solvent. Some of the solvents I tested were mineral spirits, toluene, xylene, terpentine, and methanol. Also included was the solvent I am using for The Slayer. After a half hour I removed my silicone strips, set them up on a window, and started digging into them with my thumbnail. I also had a strip that hadn't been soaked in anything. The solvent that won the contest was the one that I now use in The Slayer. It is so effective at softening cured silicone caulk that I could easily dig off huge chunks of caulk with my nail. The other solvents didn't even come close. From this I figured if I could also find an equally effective optical grade microcrystalline polishing powder that would blend well with this solvent, I would have a true Silicone Slayer!
The powder of choice (but not the only one that can be used) turned out to be an optical grade silicon dioxide, a silica. It has an average particle size of 99.9% purity at about five microns. The morphology was amorphous. The outer surface of the particles were treated with a hydrophillic surfactant helping to bring them quickly into a water based solution. So since the molecular polarity of my solvent was such that it also would disperse well in water, the solvent and this powder went together well. In theory and practice. The Silicone Slayer has become a very effective tool in my work.
Written by Henry Grover Jr
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