Creosote

Part of Petroleum and Tar

Producing and using creosote for wood preservation and other applications in a rebuilding society.

Why This Matters

Wood is the most accessible structural material in any rebuilding scenario, but untreated wood rots, attracts insects, and deteriorates within years when exposed to moisture and soil contact. Creosote — a dark, oily liquid derived from the destructive distillation of wood tar or coal tar — is one of the most effective wood preservatives known to humanity. Railroad ties treated with creosote have lasted over a century in service, and fence posts treated with it outlast untreated ones by five to ten times.

In a world without access to modern chemical preservatives like chromated copper arsenate (CCA) or pressure-treated lumber, creosote becomes your primary defense against wood decay. Every bridge timber, dock piling, fence post, and foundation sill that contacts soil or water will benefit enormously from creosote treatment. The difference between a structure lasting five years and one lasting fifty years often comes down to whether the wood was properly treated.

Creosote production requires no exotic materials — only wood, a sealed retort or kiln, and the knowledge of how to collect and refine the condensate. The same process that produces charcoal can be modified to capture creosote, making it a natural byproduct of an operation you may already be running.

Understanding Creosote

Creosote is not a single chemical but a complex mixture of hundreds of organic compounds produced when organic material undergoes pyrolysis — heating in the absence of oxygen. The two main types relevant to a rebuilding society are wood-tar creosote and coal-tar creosote.

Wood-tar creosote comes from the destructive distillation of hardwoods or resinous softwoods. It contains phenols, cresols, guaiacol, and creosol — compounds that are toxic to the fungi and insects that destroy wood. This is the type you will most likely produce first.

Coal-tar creosote comes from the carbonization of coal and contains polycyclic aromatic hydrocarbons (PAHs), phenols, and heterocyclic compounds. It is a more potent preservative but requires access to coal and more sophisticated distillation equipment.

Property	Wood-Tar Creosote	Coal-Tar Creosote
Source	Hardwood/softwood pyrolysis	Coal carbonization
Color	Dark brown to black	Dark brown to black
Smell	Smoky, sharp	Pungent, tarry
Preservative strength	Good	Excellent
Ease of production	Simple	Requires coal + more equipment
Toxicity	Moderate	Higher

Health Precautions

Creosote is a skin irritant and suspected carcinogen with prolonged exposure. Always wear gloves when handling it, avoid skin contact, and never use creosote-treated wood for food preparation surfaces, drinking water containers, or indoor applications where people will breathe the fumes regularly.

Producing Wood-Tar Creosote

The production process is essentially a modification of charcoal making, where instead of letting the volatile gases escape and burn, you capture and condense them.

Building a Retort System

1. The retort vessel: Use a metal drum, large clay pot, or stone-lined chamber that can be sealed. The vessel must have a single exit pipe for gases but otherwise be airtight.

2. The exit pipe: Fit a metal or ceramic pipe (2-4 cm diameter) into the top or upper side of the retort. This carries the hot gases to the condenser.

3. The condenser: Run the exit pipe through a trough of cold water or wrap it in wet cloth that you keep saturated. The pipe should descend at a gentle angle. As hot gases pass through the cooled pipe, they condense into liquid.

4. The collection vessel: Place a jar or bucket at the end of the condenser pipe to catch the liquid condensate.

The Distillation Process

1. Fill the retort with wood — hardwoods like oak, beech, or hickory produce the best creosote, though pine and other resinous softwoods also work well.
2. Seal the retort, ensuring gases can only exit through the condenser pipe.
3. Build a fire around or beneath the retort. Heat slowly at first — too rapid heating cracks the vessel and produces inferior product.
4. As the wood heats past 200°C (390°F), pyrolysis begins. You will see liquid dripping from the condenser into your collection vessel.
5. The first liquid is mostly water with dissolved acetic acid (pyroligneous acid). This is useful but is not creosote.
6. As temperature rises past 300°C (570°F), the condensate darkens and becomes oily. This is the creosote fraction.
7. Continue heating until no more liquid flows — typically 6-12 hours depending on the size of your charge.

Separating the Fractions

The raw condensate separates naturally into layers if left to settle:

• Top layer: Watery pyroligneous acid (acetic acid, methanol, acetone) — save this for other uses
• Bottom layer: Dark, oily creosote — this is your wood preservative
• Settled tar: Very thick residue at the bottom — this is wood tar, also useful

Carefully decant or siphon off each layer. The creosote layer has a distinctive smoky smell and an oily consistency thinner than tar but thicker than water.

Applying Creosote to Wood

The effectiveness of creosote treatment depends heavily on how deeply it penetrates the wood. Surface brushing provides minimal protection; deep penetration provides decades of service.

Methods of Application (Least to Most Effective)

Brushing or spraying: Apply creosote liberally to the wood surface with a brush or rag. Apply multiple coats, allowing each to soak in before adding the next. This provides 2-5 years of additional service life. Best for large timbers that cannot be soaked.

Cold soaking: Submerge the wood in a trough of creosote for 24-72 hours. The creosote penetrates the end grain and any checks or cracks. Provides 10-20 years of protection. Build a soaking trough from stone or lined earth.

Hot-and-cold bath: This is the most effective method available without pressure equipment.

1. Heat creosote in a metal vessel to about 90°C (195°F) — hot but not boiling.
2. Submerge the wood in the hot creosote for 2-4 hours. The heat expands the air in the wood cells.
3. Remove the wood and immediately submerge it in cold creosote.
4. As the wood cools, the air in the cells contracts, creating a partial vacuum that draws creosote deep into the wood.
5. Leave submerged for 12-24 hours.

This method can achieve penetration depths of 15-25 mm, comparable to early industrial pressure treatment.

Maximize Penetration

Always treat wood that has been seasoned (dried) rather than green wood. Dry wood absorbs far more creosote. Peeling the bark also dramatically improves absorption, as bark acts as a natural barrier.

Treatment Priority Guide

Not all wood in a structure needs creosote treatment. Focus your limited supply on:

Priority	Application	Why
Highest	Ground-contact posts, pilings	Direct soil/water contact causes fastest rot
High	Bridge timbers, dock structures	Constant moisture exposure
Medium	Sill plates, floor joists near ground	Splash zone and humidity
Lower	Fence rails, exterior siding	Some moisture but above ground
Lowest	Interior framing, roof structure	Minimal moisture if roof is sound

Other Uses for Creosote

Beyond wood preservation, creosote has several valuable applications:

Antiseptic and disinfectant: Dilute creosote solutions were historically used to disinfect wounds and treat skin conditions. While modern medicine has moved away from this, in a survival context, a very dilute creosote wash can help prevent wound infection when nothing better is available.

Animal husbandry: Creosote can be used to treat fence posts in animal enclosures and to discourage wood-chewing by livestock. A thin application on wooden structures deters termites and boring insects.

Rope and cordage preservation: Soaking ropes in dilute creosote extends their service life significantly, particularly for ropes used in wet environments like well ropes or dock lines.

Torch and fire-starting material: Creosote-soaked rags or wood shavings make excellent fire starters and long-burning torches.

Yield Expectations and Storage

A typical hardwood charge yields roughly:

• 25-30% charcoal by weight
• 35-45% pyroligneous acid (watery condensate)
• 5-10% creosote and tar
• 20-30% non-condensable gases (lost)

From 100 kg of dry hardwood, expect approximately 5-8 liters of usable creosote. This is enough to treat 10-15 fence posts by the hot-and-cold bath method, or to brush-treat a much larger number of timbers.

Store creosote in sealed containers away from heat and flame. It keeps indefinitely if protected from evaporation. Glass, glazed ceramic, and metal containers all work well. Never store in unglazed pottery, as the creosote will slowly seep through.

Fire Hazard

Creosote is flammable. Never heat it over an open flame — always use indirect heat or a water bath. Keep storage containers away from fires and sparks. Rags soaked in creosote can spontaneously combust if wadded up; always spread them flat to dry or submerge them in water.

Troubleshooting Common Problems

Condensate is mostly water: Your retort temperature is too low. Increase heat gradually. The creosote fraction comes at higher temperatures.

Very low yield: The wood may be too wet. Season wood for at least 6 months before distilling. Green wood wastes fuel driving off moisture before pyrolysis begins.

Creosote does not penetrate well: The wood may be too green, still have bark, or be a species with naturally low permeability (like white oak heartwood). Try the hot-and-cold bath method with well-seasoned, peeled wood.

Treated wood still rots: Surface treatment alone is insufficient for ground contact. Only the hot-and-cold bath method provides adequate penetration for soil contact applications. Reapply surface treatments every 2-3 years.