water glass

[hughie]

Found this while wasting time on the net

View: https://www.youtube.com/watch?v=7J7gkxYCgL0


Thoughts folks

 

[Doug Freeman]

Some of the old treatments/chemicals can still have a good use. Calcium soap is one - WW2 and earlier used on Navy ships for rust prevention. My source is Lee Alox Bullet Lube, thinned ~20:1. This one not so much for wood. AI info:

“Sodium silicate” (often called water glass) absolutely was used on wood in the late 1800s through mid-1900s—but it faded out for some very practical reasons.

What it did (and why people liked it)​

6

Back then, it was attractive because it was:

• Cheap and widely available
• Non-flammable
• Somewhat insect- and mold-resistant
• Added limited fire resistance (it forms a mineral-like layer)

Chemically, it soaks into wood pores and dries into a glassy silica network—basically turning part of the surface into something closer to mineral than organic.

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Why it fell out of favor for wood​

Short version: it kind of worked, but modern chemistry works far better.

1) Moisture sensitivity (biggest issue)​

• Sodium silicate is water-soluble again after curing (especially with humidity exposure).
• That means:
  • It can leach out over time
  • Protection isn’t permanent outdoors
• Compared to modern sealers, it’s not a true waterproofing system

2) Surface problems​

• Leaves a brittle, chalky/glassy film
• Can:
  • Crack
  • Flake
  • Create a rough feel
• Not great for anything you want to look good or last structurally

3) Poor durability vs modern options​

By the 1940s–1960s, better treatments showed up:

• Oil-based preservatives (e.g., creosote, pentachlorophenol)
• Pressure-treated lumber (CCA, later ACQ, etc.)
• Modern polymer sealers and epoxies

Those:

• Penetrate deeper
• Stay in place
• Handle weather cycles far better

4) Limited biological protection​

• It’s mildly resistant to fungi/insects, but not nearly as effective as modern preservatives
• It doesn’t actively kill organisms the way later chemicals do

5) Alkalinity issues​

• Highly alkaline → can:
  • Damage finishes applied over it
  • Cause long-term fiber degradation in some conditions

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Why it is still used (just not much on wood)​

5

It didn’t disappear—it just found better applications.

Concrete (where it shines)​

• Reacts with calcium hydroxide in concrete → forms calcium silicate hydrate (C-S-H)
• That:
  • Hardens the surface
  • Reduces dusting
  • Improves durability

This is why it’s still common as a concrete densifier/sealer

Other uses​

• Fireproof coatings (industrial)
• Refractory cements
• Egg preservation (old-school trick)
• Adhesives and binders

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Is it used on wood today at all?​

Very niche:

• Some DIY fire-retardant treatments
• Occasional use in historic restoration
• Experimental “mineralization” treatments

But in real-world construction or woodworking?
It’s basically obsolete.

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Bottom line (straight answer)​

Sodium silicate fell out of use on wood because:

• It doesn’t stay stable with moisture
• It forms a brittle, mediocre protective layer
• It was outclassed by pressure treatments and modern sealers

It survived in concrete because the chemistry there actually improves the material permanently, instead of just coating it.