What the sources say about making your own
| Approach | What it relies on | What the source says | Caution |
|---|---|---|---|
| The Madison formula (1950s) | Linseed oil, pigment and the fungicide pentachlorophenol | It can no longer be made: the fungicide is unavailable to the public | Linseed-oil finishes without a fungicide are prone to mildew |
| A homemade water repellent | Varnish, wax and solvent | Performs poorly against commercial ones; the author would not use it on his own home | The Laboratory itself warns of extreme fire danger in mixing it |
| Iron on tannin-rich wood | Iron reacting with the wood's tannin-like extractives | Gives a blue–black colour; ink was made this way for centuries | Documented as a defect; no recipe is given |
| A commercial semitransparent stain | Alkyd-modified oil, pigment and fungicide | The Laboratory's recommendation over homemade finishes | Follow its label |
From the Forest Products Laboratory's FinishLines 'Alternatives to the Madison Formula' and 'Iron Stain on Wood' (2013).
The Madison formula, and why it is retired
The Forest Products Laboratory developed the Madison formula around 1950 as a simple linseed-oil finish anyone could mix: with pigment it was a semitransparent stain, without it a water repellent. Its critical ingredient was pentachlorophenol, a fungicide that, the Laboratory explains, has not been sold to the public since the mid-1980s and has no suitable substitute — so the formula can no longer be made. Linseed oil without a fungicide, it adds, is food for mildew. Its conclusion is direct: many modern commercial finishes are better than the Madison formula, and commercial finishes should be used rather than homemade ones. For what to look for in a bought stain, see choosing a stain.
Iron and tannin
The other homemade route is a reaction in the wood. The Laboratory's FinishLine on iron stain explains that iron reacts with tannin-like extractives in wood to give a blue–black or grey colour; oak, redwood, cypress and cedar, rich in those extractives, are the most prone, and ink was made for centuries by mixing tannin and iron in solution. Woodworkers use the same reaction on purpose to darken tannin-rich woods. The Laboratory documents it as a stain to avoid — from steel wool, wire brushes, iron tools or rusty containers — and gives no recipe, so none is given here. What it does establish is useful for anyone trying it:
- It needs water. The reaction happens when moisture brings iron and extractives together; wood kept dry does not discolour.
- It depends on the wood. The result follows the wood's own tannin content, so it varies between species and between boards. Test on the project's own offcuts.
- It can be reversed, partly and temporarily. Oxalic acid removes iron stain, the Laboratory says, but staining returns if iron remains, and on oak the acid can leave a pink stain if left too long.
- The remover is hazardous. The Laboratory warns that oxalic acid can irritate and burn skin, eyes and mucous membranes and that swallowing a few grams can be fatal; use it only as its label directs.
- Iron in the wrong place stains too. Steel wool used between coats on tannin-rich wood is one of the sources the Laboratory names.
The project: a stain sample board
Whatever stain you use, bought or otherwise, the colour on the can is not the colour on your wood. Minwax notes that wood varies in colour and pore structure even within one species and tells users to test first. A sample board does that properly, and shows at the same time what a conditioner, a second coat and the topcoat will do.
Making a sample board
Cut it from the project's wood
An offcut of the same boards, at least a hand's width wide and long enough for four areas side by side.
Prepare it like the project
Sand to the same grit, in the same way — see how to sand wood and, for the abrasives, choosing sandpaper. A board sanded differently will not stain the same.
Condition half
Treat two of the four areas with the conditioner meant for your stain's base, on its maker's timing; leave two bare. The choice of conditioner is in how to stain wood.
Stain in one and two coats
Apply and wipe exactly as you will on the piece; give one bare and one conditioned area a second coat after the maker's recoat time.
Topcoat half
Once the stain is dry for its maker's time, put your intended topcoat across the lower half: it changes the colour again.
Label and judge it dry
Write on the back what went on each area. Look at it dry, under the light the piece will live in, before choosing.
Keep the board with the finished piece; it records the schedule for touch-ups. If the wood blotches whatever you do, the Forest Products Laboratory notes one cause no conditioner fixes — infection of the lumber before it was dried. For stain types see wood stain; for rags and ventilation, finishing techniques.
Making a stain sample board
- An offcut of the project's own wood
- Sanded to the same grit as the project
- Conditioned and bare areas, one and two coats
- The intended topcoat over half the board
- Each area labelled on the back
- Judged dry, in the room's light
Sources
Homemade stains are described only as the Forest Products Laboratory documents them. No recipes are given: the Laboratory gives none for iron staining, says its own stain can no longer be made, and its author advises against the one homemade water repellent he describes. Kitchen stains such as coffee or tea were not covered by any source reviewed and are not described.
- 1.
Mark Knaebe. Alternatives to the Madison Formula, the Original Do-It-Yourself Semitransparent Stain (FinishLine). USDA Forest Service, Forest Products Laboratory, 2013.
Used for: The Madison formula as a linseed-oil-based penetrating finish developed at the Laboratory around 1950, made with pigment as a semitransparent stain; pentachlorophenol as its critical fungicide, unavailable to the public since the mid-1980s, so that the formula can no longer be made; homemade water repellents performing poorly against commercial ones; the Laboratory's advice to use commercial finishes; film-forming 'stains' being really paints.
- 2.
Mark Knaebe. Iron Stain on Wood (FinishLine). USDA Forest Service, Forest Products Laboratory, 2013.
Used for: Iron reacting with tannin-like extractives to give a blue–black discoloration, especially on oak, redwood, cypress and cedar; ink made for centuries by mixing tannin and iron; steel wool, wire brushes and iron tools as sources; no discoloration while the wood stays dry; oxalic acid removing the stain temporarily, its toxicity, and a pink stain it can leave on oak.
- 3.
Christopher G. Hunt. Wood Handbook: Wood as an Engineering Material (FPL-GTR-282), Chapter 16: Finishing Wood. USDA Forest Service, Forest Products Laboratory, 2021.
Used for: Stains accentuating grain by absorbing differently into earlywood, latewood and pores; blotching from fungal or bacterial infection that cannot be corrected once stained.
- 4.
Product Data Sheet, Minwax Wood Finish (MWX132). Minwax, 2026.
Used for: Testing a stain on a hidden spot first; recoating to darken; letting the stain dry completely before a topcoat.
- 5.
Minwax Product Guide. Minwax.
Used for: Wood varying in colour and pore structure even within a species, so stain colour varies and should be tested; conditioners for woods that absorb unevenly.
About this guide
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