Oxalic Acid
Dilution Calculator
Oxalic acid ships as a solid crystalline powder that you dissolve into water for wood bleaching, deck cleaning, and rust removal. This page launches the main Alliance Chemical calculator preloaded with oxalic stock and explains the typical grams-per-gallon recipes behind the math.
Start With The Common Oxalic Jobs
Oxalic acid search intent clusters around wood bleaching (for stains and iron-tannin reactions), deck restoration, and rust removal from metal. These launchers cover all three.
10% → 5%
Preload a 1-gallon 5% solution — the common strength for removing tannin stains and iron-reaction darkening from raw wood.
Open Preloaded Calculator Deck Restoration10% → 4%
Build a 5-gallon 4% deck-cleaning solution for greying and mildew restoration before sealer or stain reapplication.
Open Preloaded Calculator Gentle Revival10% → 2%
Lighter 2% solution for delicate wood, soft stone, or composite surfaces where 5% would etch or lighten too aggressively.
Open Preloaded Calculator Ratio Mode1 : 1 Water
1:1 dilution of 10% stock into water for intermediate 5% working solutions when SOPs are written as parts.
Open Preloaded CalculatorUnderstand The Oxalic Recipe Pattern
Oxalic is sold as solid dihydrate crystals, not liquid. Real-world recipes are gram-per-gallon, but the math still maps cleanly to the percent-dilution model once you treat a 10% w/v solution as the starting stock.
Two ways to mix oxalic. Option A: dissolve the target grams of crystals directly into your final water volume — simplest when you already know the target percentage. Option B: make a 10% w/v stock solution once and dilute from it — useful when you batch recipes frequently and want consistent math.
Typical grams-per-gallon recipes. A 5% wood-bleaching solution is roughly 190 g of oxalic dihydrate per gallon of water. A 4% deck wash is ~150 g/gal. A 2% gentle solution is ~75 g/gal. The calculator above uses the stock-and-dilute model, but these direct weights work identically.
Which product. Dihydrate is the standard crystal form — what most wood-working and restoration recipes assume. ACS Grade is the purer laboratory form, useful when you need reproducibility or documentation for analytical work.
Filter the stock. Oxalic crystals dissolve well in warm water but leave fine particulate that can clog sprayer nozzles. Strain the stock solution before loading a pump-up sprayer or HVLP gun.
Common Oxalic Dilution Targets
Working strengths depend on substrate and severity. Start at the lighter end and step up only if the first pass is under-performing — oxalic will lift wood color permanently.
| Starting Stock | Target | Typical Use | Notes | Launch |
|---|---|---|---|---|
| 10% w/v stock | 5% | Wood bleaching and tannin stain removal | Standard target for raw-wood restoration and iron-reaction stain removal. Typical recipe: ~190 g oxalic per gallon water. | Open |
| 10% w/v stock | 4% | Deck cleaning before refinishing | Common concentration for greyed or mildew-darkened deck boards. Apply wet-on-wet, dwell 15 min, neutralize and rinse. | Open |
| 10% w/v stock | 2% | Gentle wood or composite refresh | Milder entry point when aggressive bleaching is not wanted or the substrate is soft, painted, or composite. | Open |
| 10% w/v stock | 1:1 water | Intermediate step-down from stock | Halves the stock to 5% in equal-parts-water mode, matching SOPs written as parts rather than percent. | Open |
Oxalic Handling Reality Check
Oxalic acid is toxic if swallowed and aggressive on eyes and skin despite the mild-sounding wood-bleach marketing. Dust inhalation during weighing is the most overlooked hazard.
Dust matters more than liquid. The most common oxalic exposure is inhalation during weighing and mixing. Wear a dust mask rated for fine particulates (P100 or equivalent) when handling the dry crystals; switch to liquid-phase handling once dissolved.
Neutralize and rinse, always. Residual oxalic left in wood grain or sprayer lines will continue reacting. Neutralize with a baking-soda wash after treatment, then rinse thoroughly. Especially important on decks before sealer application.
Compatible with most woods; variable on stone. Oxalic is the standard wood-bleaching acid. On stone, it is excellent for iron-stain removal but can etch calcium-rich materials (limestone, marble, some concrete). Test a hidden area first.
Store dry and sealed. Oxalic crystals are hygroscopic — they will cake in open containers exposed to humidity. Keep the bag sealed between uses, or transfer to a tight-sealing plastic container.
Related Internal Resources
Use these pages to compare acids, understand adjacent use cases, and route visitors deeper into the resource center instead of bouncing back to search.
Frequently Asked Questions
Visible answers that match the search intent this page is targeting.
FAQ
How much oxalic acid do I use per gallon of water?
Does oxalic acid bleach wood color permanently?
What is the difference between dihydrate and ACS oxalic acid?
Can I use oxalic acid on stone or concrete?
Need Oxalic Acid For Wood Or Rust Work?
Buy dihydrate for standard restoration recipes, or step up to ACS Grade when documentation and trace-level purity matter.