Fireproofing with liquid glass: impregnation of wood with sodium silicate

Wood is a warm and technological material, but combustible. One of the available ways to reduce its fire vulnerability is fire protection with liquid glass, that is, impregnation of the surface with a solution of sodium silicate. The method has long been used in private construction and farming: it is inexpensive, easy to apply and in addition works as an antiseptic. Let's see how it works physically and where the boundary of reasonable use lies.

How liquid glass protects wood from fire

Sodium liquid glass is an aqueous solution of sodium silicate obtained from natural raw materials (quartz sand and soda). When applied to wood, the solution penetrates into the surface layer and pores, and after drying, the water evaporates and a solid mineral film of silicate remains. This film is on its own Non-Flammable.: Silicate is a mineral substance, it does not support combustion.

The fire protection mechanism consists of several effects:

• Barrier film. The silicate layer blocks oxygen access to the wood fibers, slowing the ignition of the surface.
• Heating swelling. At high temperature, sodium silicate is able to soften and foam, forming a porous heat-insulating layer that temporarily cuts off the flame from the wood.
• Filling of pores. Impregnation reduces the capillarity of the surface, which is why wood absorbs and retains what supports combustion worse.

It is important to understand honestly: liquid glass does not make wood "non-flammable". It increases the fire resistance and slows down the flame propagation at an early stage — this is a protection of the class "make it difficult to start a fire", and not absolute non-combustibility.

Fireproofing plus antiseptic: two effects in one

A nice bonus of silicate impregnation is antiseptic properties. Sodium silicate suppresses mold, fungus and putrefactive processes, and the alkaline environment is unfavorable for microorganisms and part of the woodpecker insects. Therefore, one treatment solves two problems at once: it reduces flammability and protects wood from biohazard. For rafters, rough floors, logs, crates in dry rooms, this is a practical combination.

Indicative proportions and flow

We will not give exact "iron" recipes — they need to be specified according to the instructions and the task. Below are the indicative values, from which it is convenient to build.

The indicative indicators of the material itself are typical for sodium liquid glass: silicate module of the order of 2.6-3.4; density of about 1.4 g/cm³. Refer to the ETHYZ product data sheet for exact values. Sodium liquid glass is standardized according to GOST 13078.

Procedure for application to wood

1. Preparation Wood should be dry and clean: remove dust, old coatings, resin. Impregnation on raw wood does not hold well.
2. Dilution Prepare a solution of the desired concentration (approximately 1:2–1:3), mix thoroughly.
3. First layer Apply with a brush, roller or sprayer along the fibers, trying to impregnate the surface evenly.
4. Drying. Allow the layer to dry (follow the instructions and conditions — usually a few hours).
5. Repeated layers. Apply 2–3 coats to form a continuous film.

You need to work quickly and in small areas: the liquid glass sets rapidly, the tools and containers are immediately washed with water after work. In its pure form, the frozen film turns out to be solid, but fragile — when deformed and vibrated, it may crack. Use hand and eye protection: alkaline solution.

Limitations of the method — honestly

Liquid glass is a good household solution, but it has a scope of applicability:

• It is not a certified flame retardant for critical structures. For load-bearing elements, evacuation routes, facilities with requirements for the fire-retardant efficiency group, specialized compositions with test reports are required. Silicate impregnation does not replace them.
• The film is fragile. On surfaces prone to abrasion and bending, the protective layer breaks down over time and requires renewal.
• Finishing on top is limited. Many varnishes and paints on organic binders do not fit well on the silicate film — compatibility should be checked.
• Not for permanently wet areas outside. Direct rain washing gradually reduces protection.

The correct position: use liquid glass where you need inexpensive basic protection of hidden wooden elements from fire and rot (attics, underground, outbuildings, rough structures), and do not replace them with certified fire protection where it is required by the norms.

Pre-packing and selection of ETHYZ product

ETIZ liquid sodium glass is a universal silicate concentrate for construction, waterproofing and material processing. Available in convenient packaging: cans of 5 l (7 kg) and 10 l (14 kg). For flame retardant and antiseptic treatment of wood, this is the same sodium silicate — only the degree of dilution for the task changes. For more information about the product and characteristics, see the catalog: Liquid glass.

If you doubt the concentration or compatibility with the subsequent finishing, refer to the instructions for a particular batch and material data sheet. And for comparison of packages and clarification of properties, it is convenient to immediately look at liquid glass section.

FAQs

Is it possible to completely protect the house from fire with liquid glass?

No. Fireproofing with liquid glass reduces the flammability of wood and slows ignition at an early stage, but does not make wood non-combustible. This is the basic household protection for hidden and rough elements. For load-bearing structures, evacuation routes and objects with regulatory requirements for the fire protection group, certified flame retardants with test reports are needed — silicate impregnation does not replace them.

How to dilute liquid glass for impregnating wood?

Approximately, the concentrate is diluted with water in a ratio of 1:2–1:3, but the exact values should be specified according to the instructions for a particular batch and according to the task. A weaker solution penetrates deeper into the fibers, a more concentrated one gives a dense surface film. Usually 2–3 layers with intermediate drying are applied. The proportions given are indicative, not a hard recipe.

Does liquid glass only protect the wood from fire?

No, the effect is double. In addition to reducing flammability, sodium silicate works as an antiseptic: it suppresses mold, fungus and putrefaction, and the alkaline environment is unfavorable for microorganisms. Therefore, one treatment simultaneously increases the fire resistance and protects the wood from biodegradation — this is convenient for rafters, logs and crates in dry rooms.

Why does the liquid glass film crack?

The solidified sodium silicate in its pure form forms a hard but brittle film. When the wood is bent, vibrated, shrunk or abraded, it can crack and crumble. Therefore, it is better to use silicate impregnation on sedentary hidden elements and periodically update it. On mechanically loaded surfaces, the protective layer serves less and requires control.

What liquid glass does ETHYZ produce for wood processing?

ETIZ produces sodium liquid glass — a universal aqueous solution of sodium silicate for construction, waterproofing and processing of materials, including wood. Potassium glass (more often for paints and flame retardants) is not positioned in this line. Packing — cans of 5 l (7 kg) and 10 l (14 kg). The same sodium silicate diluted for the task is used for fire protection of the tree.