Sinking vs Floating Agarwood: Density, the Water Test and What a Strand Should Weigh

Sinking agarwood is agarwood dense enough to sink in water, and the name doubles as a physics lesson. In Chinese, agarwood is chénxiāng, “sinking fragrance”. The most resin-rich pieces weigh more than water, so the pieces go to the bottom of a bowl. For centuries, sink or float was the simplest grade there was.

Yet “sinking agarwood” is also one of the most misused phrases in the trade. Some agarwood sellers print “sinking” on strands that would bob on the surface of a teacup. Others recommend the water test as a way to spot fakes, which the test is not.

AgarwoodTown has traded agarwood since 2014, and Oudbracelet is the shop for single strands. We weigh every strand on camera, so we work out density every day.

The guide sticks to what you can check yourself. First, Part 1 covers density and resin. Next, Part 2 shows how to calculate density from a weight and a bead size. Then Part 3 covers what the water test can and cannot tell you. Finally, Part 6 explains how we handle the rare sinking agarwood strands. Choosing a bracelet from scratch? Then the buying guide is a better place to start.

Wood floats when wood density is below the density of water, 1.0 g/cm³, according to Forest Products Laboratory data in the 2010 Wood Handbook.^{(USDA 2010)} Most agarwood floats, and sinking agarwood stays rare in plantation strands.

The chooser splits sinking agarwood questions into two groups. First, pick what you want to find out: the density of a strand, whether a strand is genuine, why weight sets the quote, or whether a sinking grade is available. Second, pick the wood you lean towards. For example, dark agarwood suits a buyer who wants resin-heavy beads, while pale agarwood shows clear grain lines. Additionally, loose agarwood beads are the safest way to try a water test, because a loose bead has no cord to soak.

Density is mass packed into a volume, measured in grams per cubic centimetre. Fresh water sits at about 1.0 g/cm³. Anything denser sinks in water, while anything lighter floats, as Archimedes showed.

Wood is mostly cell walls around empty space. The wall material itself weighs more than water. However, hollow cells and pores full of air pull the average down, so most woods float, according to Forest Products Laboratory data.^{(USDA 2010)} Agarwood starts life the same way, as the pale, light wood of an Aquilaria tree. When something wounds the tree, the tree defends the wound. Slowly, over years, the tree lays down a dark, aromatic resin around the damage, as a 2019 review by Tan and colleagues describes.^{(Tan 2019)} The resin fills space that used to hold air. So the volume stays the same while the mass grows, and the density climbs.

Only when resin fills enough space does a piece cross 1.0 g/cm³ and become sinking agarwood. Most agarwood never gets there, including most good plantation wood. After all, resin forms in streaks and patches rather than evenly through the wood. For example, two beads from the same log can behave differently in water.

Density is the number that decides sinking agarwood, and you do not need water to find density. Instead, you need a strand’s weight and volume. For round beads, the volume is plain geometry: a sphere with a 2 mm hole drilled through. The same formula sits behind our density check and our wrist fitter.

Here is a worked example from our own weighing sheet. 16 beads of 12 mm hold about 13.87 cm³ of wood. If the strand weighs 11.8 g, the density is 11.8 ÷ 13.87 = 0.85 g/cm³. The result marks a good, dense strand, but the strand still floats. To count as sinking agarwood, the same strand would need to weigh more than about 13.9 g.

Two details catch people out. The first is the hole. On a 12 mm bead, the 2 mm channel removes about 4% of the sphere. Forget the hole, and the same strand works out at 0.82 instead of 0.85.

The second is everything other than wood. Cord, spacers, stones and metal fittings all add weight without adding agarwood. So the arithmetic only stays clean for a pure agarwood strand of round beads. For other cuts, ask the seller for the bead dimensions, or simply use strand weight to compare like with like.

The sinking agarwood water test is the classic home check, and the test appeals because the result looks like proof. You drop a bead in and watch. In practice, however, the test answers a narrower question than people think: is the bead, right now, denser than the water in the glass? Several things can also bend the answer.

Air in the hole. A drilled bead traps air in the channel. So a bead only just denser than water can float until the bubble works out.

Water soaking in. Wood takes up moisture and gets heavier, according to Forest Products Laboratory data.^{(USDA 2010)} As a result, a bead left in water for a long time can drift down and read as denser than the dry bead.

What is in the water. Salt raises the density of water, so a borderline bead that sinks in tap water may float in brine. Soap and oils, meanwhile, change how the surface holds a small bead.

Size. A single 12 mm bead holds about 0.87 cm³, so a single bead sinks only above roughly 0.87 g. A kitchen scale that reads to the gram cannot see the difference.

None of the four problems makes the water test useless. A clear sink or a clear float tells you something. Anything in between is better settled with a scale.

Density is a measure of one thing: how much mass the wood carries for the size. In genuine agarwood, extra mass mostly means extra resin, so density offers a sensible way to compare strands. Other things can add mass too. For example, someone can weight, soak or inject wood, and a treated bead can sink as convincingly as real sinking agarwood. Equally, a bead that floats may be perfectly genuine plantation agarwood with modest resin.

So treat a sink or a float as one piece of evidence among several. First, compare the density with the grain under magnification. Second, warm a bead and check the scent. Finally, ask whether the seller will show you the actual piece on video. Our guide to telling real agarwood covers each check and the limits of each one.

Sinking agarwood is rare, and floating agarwood is almost everything on the market. Neither column proves a bead genuine. For example, weighted wood can sink, while honest plantation wood with modest resin floats. The real difference is resin: sinking wood carries resin through most of the wood, and floating wood carries resin in streaks. In practice, the scale separates a dense floating strand from a borderline sinking strand better than the eye does. Additionally, every style on the site floats, and we quote sinking strands separately, on request.

Sinking agarwood is uncommon in plantation wood, because plantations do on purpose what happens by accident in the wild. Growers wound cultivated trees so the trees form resin. Studies of induced Aquilaria sinensis report resin chemistry close to wild agarwood, according to Liu and colleagues in 2013.^{(Liu 2013)} Still, whether a piece turns into sinking agarwood depends on how much resin the individual piece holds.

Sinking is also only one part of how the trade grades agarwood. Grading systems in the research literature look at resin content, oil and chemical markers, plus appearance and density, as a 2021 review by Wang and colleagues sets out.^{(Wang 2021)} So a strand is not simply “sinking” or “worthless”. In fact, most of the interesting wood lives in the floating bands, from mid to dense.

Sinking agarwood is the top of a density range, not a line between good and bad. “Sinking fragrance” is a beautiful name, and the physics behind the name is real: resin fills the wood, and the wood grows heavy. Most agarwood worth wearing floats rather than sinking. A strand’s character does not switch on at 1.0 g/cm³, either. Grain, warm scent and the way the wood darkens with years of wear matter just as much.

So let the scale do the work the water test always tried to do. First, ask for the weight, the bead size and the bead count. Second, do the division. For example, the 12 mm strand in Part 2 weighs 11.8 g and works out at 0.85 g/cm³, dense but floating. Finally, judge the rest with your eyes and nose.