Nitrocellulose lacquer is a finish made by dissolving nitrocellulose (a treated cotton fiber) in a blend of fast-evaporating solvents, then adding plasticizers and resins to improve the final film. Unlike varnishes or polyurethanes, it dries entirely by solvent evaporation with no chemical reaction, which is what gives it that signature quick-drying quality and the ability to be re-dissolved and repaired. Understanding the core ingredients and how they interact is the key to formulating a working lacquer.
The Four Core Ingredients
Every nitrocellulose lacquer contains the same basic categories of ingredients: the nitrocellulose itself, true solvents that dissolve it, diluents that thin the mixture without dissolving nitrocellulose on their own, and plasticizers or resins that make the dried film flexible and durable. A classic formulation uses roughly 16 ounces of nitrocellulose and 16 ounces of resin dissolved in one gallon of mixed solvents. The ratio between solids (nitrocellulose plus resin) and solvents determines how thick the lacquer sprays and how much film builds up per coat.
The nitrocellulose provides the hard, clear film. Resins like dammar gum, shellac, or synthetic alkyd resins add gloss, depth, and adhesion. The solvent blend controls how fast the lacquer dries, how well it flows out, and whether it develops defects like blushing (a milky haze caused by trapped moisture). Plasticizers keep the dried film from becoming brittle and cracking over time.
Choosing the Right Nitrocellulose Grade
Nitrocellulose comes in two main grades that behave differently in a formula. SS grade (called “Spirit Soluble” in the US, or Grade A in Europe) has a nitrogen content of 10.7 to 11.3 percent and dissolves in alcohols, esters, ketones, and glycol ethers. RS grade (“Regular Soluble,” or Grade E in Europe) has higher nitrogen at 11.8 to 12.3 percent and dissolves only in esters, ketones, and glycol ethers. Alcohols can be used to thin RS nitrocellulose but won’t dissolve it on their own.
For most wood finishing lacquers, RS grade is the standard choice. It produces a harder, more durable film. SS grade finds more use in specialty coatings where alcohol solubility is needed. Nitrocellulose is always sold dampened with water or solvent because it is extremely flammable when dry. You should never let it dry out in storage.
Building the Solvent Blend
The solvent system is the most complex part of the formula and the piece that determines how the lacquer performs in real-world spraying conditions. Solvents are grouped by boiling point into three tiers, and a good lacquer uses a mix from each.
- Low boilers (below 100°C): Ethyl acetate is the primary nitrocellulose solvent in this range, with ethyl alcohol serving as a diluent. These evaporate first and give the lacquer its initial flash-off speed.
- High boilers (100 to 140°C): Butyl acetate and amyl acetate dissolve nitrocellulose, while butanol and toluene work as diluents. These control flow and leveling as the film forms.
- Super-high boilers (140 to 180°C): Diacetone alcohol is a common solvent in this range, with xylene as a diluent. These evaporate last and give the film time to level out smoothly before it sets.
A typical one-gallon solvent blend might break down as: 30 percent ethyl acetate, 10 percent diacetone alcohol, 10 percent butanol, 25 percent toluene, and 25 percent xylene. The exact ratios shift depending on your application method, ambient temperature, and humidity. In warm, dry conditions you can lean heavier on low boilers for fast drying. In cold or humid weather, you need more of the slower-evaporating solvents to prevent defects.
Preventing Blushing With Retarders
Blushing happens when moisture from humid air gets trapped in the film as the solvents evaporate too quickly. The fix is adding a small amount of retarder, a very slow-evaporating solvent that keeps the film open longer so moisture can escape. Butyl cellosolve (a glycol ether) is one of the most effective retarders, and you only need about 2 percent of the total volume. In practical terms, a couple of ounces in five gallons of lacquer is enough to stop blushing in cold, wet weather. You add more retarder as humidity increases and less in dry conditions.
Resins and Plasticizers
Nitrocellulose alone produces a film that is clear and hard but somewhat thin and brittle. Adding resins builds body, gloss, and adhesion. Natural resins like dammar gum dissolve easily in the hydrocarbon portion of the solvent blend (toluene, xylene). Shellac is alcohol-soluble, so it needs to be pre-dissolved in butanol before being added to the mix. Synthetic alternatives like maleic and alkyd resins are common in modern formulations because they offer more consistent results and better moisture resistance than natural gums.
A formula might use equal parts nitrocellulose and resin by weight, or split the resin portion between two types. For instance, one classic formula calls for 16 ounces of nitrocellulose with 8 ounces of dammar gum and 8 ounces of shellac per gallon of solvent.
Plasticizers are high-boiling-point liquids (above 300°C) that stay in the dried film permanently, keeping it flexible. Traditional choices include tricresyl phosphate and dibutyl phthalate (DBP). However, DBP and several related phthalates are now restricted in the EU, US consumer products, and many other markets to below 0.1 percent concentration due to health concerns around hormone disruption. Safer alternatives include citrate esters, sebacates, adipates, and bio-based plasticizers derived from plant oils like castor, soy, or linseed. These newer options perform similarly without the toxicity concerns. The general recommendation from plastics engineers is to avoid plasticizers with aromatic ring structures, which are linked to endocrine disruption.
Mixing Process
The order of operations matters. Start by dissolving the nitrocellulose in the true solvent portion of the blend (ethyl acetate and any ketone or ester solvents). This can take several hours of gentle stirring. Do not shake vigorously or use high-speed mixers, as nitrocellulose is sensitive to friction and heat. Once the nitrocellulose is fully dissolved, add the resins. If you are using dammar or another hydrocarbon-soluble resin, dissolve it separately in toluene or xylene first, then combine the two solutions. Shellac should be pre-dissolved in butanol.
After the resins are incorporated, add the remaining diluent solvents (alcohols, toluene, xylene) to bring the mixture to the target viscosity. Plasticizer goes in last and mixes in easily since the solution is already fluid. Strain the finished lacquer through a paint filter to catch any undissolved particles before spraying.
Safety and Storage
Nitrocellulose lacquer and its raw ingredients are exceptionally flammable. The finished lacquer has a very low flash point, and the dry nitrocellulose itself can ignite from friction, static electricity, or heat. California’s industrial safety code (which reflects broader OSHA standards) spells out the requirements clearly: nitrocellulose must be stored in a separate, fireproof location away from any mixing or processing areas. It should never be stored in a basement. Containers must remain sealed and the material kept wet with water or solvent at all times. Frequent inspections are required to check that containers haven’t dried out or lost their seal.
No open flames, matches, cigarette lighters, or similar ignition sources should be anywhere near the work area. All equipment in the room should be metal and electrically grounded to prevent static sparks. Floors need to be smooth and free of cracks where nitrocellulose dust could accumulate. Work spaces require at least two exits, and exit paths should be kept completely clear.
Beyond fire risk, the solvents in lacquer are toxic when inhaled. Toluene, xylene, and butyl acetate all require proper ventilation or a supplied-air respirator during mixing and spraying. Skin contact should be minimized with chemical-resistant gloves.
VOC Regulations to Know
Nitrocellulose lacquer is one of the highest-VOC finishes still in use. The EPA’s current limit for lacquers, including sanding sealers, is 680 grams of volatile organic compounds per liter (5.7 pounds per gallon). That is significantly higher than the limits for most other coating categories, reflecting the reality that lacquer is almost entirely solvent by volume. Some states, particularly California under CARB rules, enforce stricter local limits. If you are formulating lacquer for commercial sale or use in a regulated facility, check your local air quality district’s rules before settling on a formula, as the allowable solvent content may be lower than the federal standard.