Mahogany Front Door Deck Sudbury

Have you noticed a change in the stain you use on your mahogany deck?  Several years ago the stain looked like, well,…stain.  Dark and oily.   You mixed it up and solids rose and lightened the oil somewhat.   You brushed it on your wood flooring, and instantly your mahogany deck took on a deep, rich color.  It soaked in and dried in a few hours.  Nice.

Old & New ATO


But the new stuff….You open the can and wonder if it is mislabeled.  It is called “Mahogany Flame”, but it has a light, milky color.  Nothing close to mahogany or anything flame-like.  What is going on here?

The Law.  Really, the culprit here is the law.   A wave of state and federal regulations is responsible for that milky amber liquid in your can.  Now wait.  Before you dump you can of stain into Boston harbor, before you start another Tea Party,…Relax.  This is not a bad law.  It did not begin in some distant city (like Washington) by some disconnected, uninformed, insensitive politicians (permanently inhabiting DC).  No.  It is based on science and began on a very local level in reaction to a very local problem.

Volatile Organic Compounds, VOC¹, refers to the gasses that stains, solvents, and other products emit which then react photochemically with the atmosphere.  Scientists know them as isocyanates.  Normal people just think “pollution”.   VOC regulation grew out of concerns about quality of the air we breathe in our cities (smog), about the wide variety of related health issues, and about depletion of the protective ozone from our atmosphere. The first regulation of VOCs began in California in the 1970s in response to the smog problems in Los Angeles.  Over time, two primary organizations have evolved to regulate lower VOC levels (separate from auto emissions): the California South Coast Air Quality Management District (SCAQMD) and the Ozone Transport Commission (OTC), formed by a coalition of northeastern states (VA, MD, DE, NJ, PA, NY, CT, RI, MA, VT, NH, ME, and DC) and recognized by the Clean Air Act Amendments of 1990.  Nationally, the EPA plays a role as well, but the strongest regulations originate at the state level.

This is undoubtedly more than you wanted to know about VOCs and government.  All you really need to know is that regulations forced the paint and stain companies to reformulate their products.  Hence:Water Based ATO 19400 OK, but will this strange looking liquid protect my deck?  Yes, but I need to explain how it works before we get to performance.  Hold on a little longer.

Oil and Water DO mix.  So to lower the VOCs, companies changed their stains.  Cabot’s first step in 2007 was to reduce the mineral spirits and increase the oil in their original series 3400 Australian Timber Oil (ATO).   This was the series 9400 that got some decidedly mediocre reviews².   In 2012 Cabot further reformulated ATO and introduced a new series, 19400, which I have tested.  This preservative stain uses water, rather than mineral spirits, to transport the oil to the wood.  I know, you thought oil and water do not mix.  So did I, but this is “water miscible” oil where the oil and water mix together at the molecular level (like mayonnaise).  So you brush the combination into the wood and the water evaporates, leaving the oil to protect the wood fibers.

OK, but how does this new ATO perform?

Well, I compared the new “water based” series 19400 ATO (with the blue cover) to the original “oil based” series 3400 on Cambara mahogany.  The results are surprising.  Take a look after three months: ATO Honey Teak at 3 months (July 2014) ATO Mahogany Flame at 3 months (July 2014) ATO Jarrah Brown at 3 months (July 2014)

And after six months:

ATO Honey Teak at 6 months (Oct 2014) ATO Mahogany Flame at 6 months (Oct 2014) ATO Jarrah Brown at 6 months (Oct 2014)

After three months, the new ATO is noticeably darker.  At six months, the difference is even more apparent:  the new “water based” ATO holds its color better than the original oil based versions.  And it performs better while polluting less.  Cool.

There’s also a subtle sub-plot here.  Look again at the three ATO stains.  The darker Jarrah Brown holds its color better than lighter Mahogany Flame, which holds its color better than the lightest Honey Teak.  What’s happening here is pigment.  Pigment solids block the sun’s UV rays, which fade wood.  So the darker stains with more pigment fade less.  Makes sense. Applying the new water based series is trickier than applying the older oil based standard.  For complete guidance on application, see my article on treating mahogany decks.  Cabot’s new stain is slower to penetrate mahogany, and you need to wipe off any excess stain within a few minutes.  And it takes longer to dry – like 8 hours or more vs. a couple of hours.

But the results are worth the wait.

At Archadeck of Suburban Boston, we offer professional design and build services for clients west and north of Boston. Over the past 27 years we have designed and built over 1,000 projects, including over 250 mahogany decks. We have enhanced the depth of our expertise by limiting our work to decks, porches, sunrooms, and patios. To view some of these projects or see our design and service awards, visit our website. To learn how we treat our clients, check our ratings on Angie’s List or read about us in an article in Remodeling magazine. For a free design consultation and a relaxed and rewarding experience, contact us via e-mail, or by phone, 781-273-3500

© 2014 Advantage Design & Constr., Inc.


  1. The US EPA defines Volatile Organic Compounds (VOC) as “Any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium carbonate, which participates in atmospheric photochemical reactions.” Thus, VOCs specifically exclude auto emissions, which are so environmentally hostile that they have earned their own long and separate history of regulations.
  2. See:
    1. The Grime Scene, Cabot ATO Problem;
    2. The Garden Web;


  1. “Key Events in the History of Air Quality in California”;
  2. From the EPA: “An Introduction to Indoor Air Quality (IAQ) – Volatile Organic Compounds (VOCs)”;  
  3. “Understanding VOC Regulations” in the Coatings Manual for HRSD Personnel.