Should You Leave the Pith in Woodturning Blanks? Why the Centre of the Tree Causes Cracks
One of the most common pieces of advice given to woodturners processing fresh logs is to paint the ends with wax, end-grain sealer or whatever leftover paint happens to be sitting in the shed.
Seal the ends, slow down the drying and the log will be fine.
Unfortunately, it is not that simple.
Sealing the end grain may slow moisture loss from the ends of a log, but it does not remove the main source of tension running through the centre of it. If the pith remains inside the wood, the log can still split badly as it dries. In many cases, it will.
The pith sits at the very centre of the tree, surrounded by wood that shrinks and moves differently as moisture leaves it. That uneven movement creates enormous internal stress. Eventually, something has to give, and the crack usually begins at the pith before travelling outwards.
This is why I nearly always remove the centre of a log before preparing bowl blanks or storing wood for later use.
The grain around the pith can be attractive. It can be tempting to keep as much of the tree as possible. Occasionally, a finished piece containing the pith may survive.
But keeping it is usually a gamble rather than good wood-processing practice.
Quick Answer: Should You Leave the Pith in a Woodturning Blank?
In most cases, no.
The pith should normally be cut out when processing logs into bowl blanks, spindle blanks or turning stock.
Wood shrinks differently across and along the grain as it dries. The wood surrounding the pith is placed under competing stresses, and cracks often begin at the centre of the tree before spreading outward.
End-grain sealer may slow drying from the cut ends, but it cannot stop the internal movement caused by leaving the pith inside the blank.
There are exceptions, particularly in thin green-turned work, small branches, hollow forms and pieces where cracking is accepted as part of the design. However, these are calculated risks rather than proof that leaving the pith is generally safe.
What Is the Pith of a Tree?
The pith is the small central core running through the trunk and branches of a tree.
It represents the tree’s earliest growth and is usually softer, less dense and structurally different from the mature wood surrounding it. In some species, it is clearly visible as a small dark or soft spot. In others, it may be harder to identify until the log is cut across.
The pith should not be confused with all of the darker wood near the centre of a tree.
Heartwood is the older, often darker wood toward the centre of the trunk. Sapwood is the younger, usually lighter-coloured wood nearer the bark. The pith is the relatively small point or line at the exact centre of growth.
However, while the pith itself may be narrow, the problem is not limited to that tiny central line.
The surrounding wood has grown in rings around it. As those rings dry and shrink, they place pressure on one another. The centre becomes the focal point for stress, and a crack can begin there before travelling through a much larger section of the log.
Why Does Wood Crack Outward From the Pith?
Freshly cut wood contains a large amount of moisture. As that moisture leaves, the wood begins to shrink.
It does not shrink equally in every direction.
Wood generally shrinks more around the circumference of the growth rings than it does across them. It also loses moisture much more quickly through exposed end grain than through the sides of a log.
These differences create tension.
Imagine a complete round log drying from the outside inward. The outer wood begins to lose moisture and shrink while the centre remains wetter and more stable. At the same time, the growth rings are trying to contract by different amounts.
The log cannot shrink evenly while remaining a complete circle.
A split forms to release the pressure.
That split very often begins at the pith because the pith sits at the centre of all those competing growth rings. Once the crack begins, it can continue travelling outward toward the bark.
This is why a log can look perfect when first cut, only to develop a deep radial split later.
It may happen within days, weeks or months depending on the species, size, weather, storage conditions and moisture content. But sealing the ends does not remove the underlying cause.
Does End-Grain Sealer Stop Logs From Cracking?
End-grain sealer has a purpose, but it is frequently expected to do more than it can.
A wax-based sealer can slow moisture loss through exposed end grain. This may reduce checking at the ends of boards, bowl blanks and sections of timber.
What it cannot do is make a complete log shrink evenly.
If the pith is still enclosed inside the log, the wood will continue to move around it. Internal stresses will still build as the heartwood, sapwood and surrounding growth rings dry at different rates.
The sealer may delay visible cracking.
It may reduce small surface checks.
It may help preserve extra length at the ends of an already well-prepared blank.
But it cannot guarantee that an intact log containing the pith will remain sound.
I demonstrate this in the opening sequence of my video on processing logs for woodturning. I seal the end grain while explaining why relying on sealer alone is largely a waste of time if the log has not first been processed correctly.
The important step is not painting the ends.
The important step is cutting the log open and removing the pith.
In the opening of this video, I seal the end grain while explaining why doing this alone will not prevent a whole log from cracking if the pith is still left inside. I created this video with new woodturners in mind so there should be some good tips.
Why Sealing a Whole Log Can Create False Confidence
The problem with the standard advice to “seal the ends and leave it” is that the log may appear fine for a while.
The ends look protected. Moisture loss has been slowed. No large crack appears immediately.
This can give the impression that the treatment has worked.
Meanwhile, stress may still be building inside the timber.
When the split eventually appears, it can run well beyond the narrow section that might otherwise have been removed during initial processing. Instead of losing an inch or two around the centre, the woodturner may lose most of the log.
A crack can also become contaminated by dirt, insects, fungal staining and moisture. Even if the timber is later cut into blanks, the damaged area may extend farther than expected.
Sealer is most useful after the timber has been divided into sensible blanks.
It should support good processing, not replace it.
How Should You Remove the Pith From a Log?
For bowl blanks, the usual approach is to cut the log lengthways through or near the pith, dividing it into two half-round sections.
The pith and a small amount of surrounding material can then be removed from each half.
This produces two potential bowl blanks, each with the former centre of the tree positioned along one flat face.
How much wood needs to be removed depends on the log.
The pith is not always perfectly centred. Trees grow around branches, lean toward light, react to wind and develop uneven tension. A line drawn through the apparent centre at one end may not follow the pith accurately along the full length.
For this reason, inspect both ends before cutting.
Look for the central point of the growth rings and imagine a line connecting the pith from one end of the log to the other. The cut should allow enough clearance to remove that complete line rather than simply touching it at one point.
Once the log is halved, trim away the pith and any visible cracking before shaping the bowl blank.
How Far Either Side of the Pith Should You Cut?
There is no universal measurement that suits every log.
For a small, straight and healthy log, removing a narrow strip around the centre may be enough. For a large trunk, stressed tree or piece with visible cracks, considerably more may need to be removed.
Do not focus only on the soft central dot.
Look at the surrounding wood.
If cracks are already radiating outward, continue cutting until they have completely disappeared. A hairline crack visible on the surface may extend much deeper than it first appears.
Reaction wood, bark inclusions, staining and irregular growth near the centre may also make the area unsuitable for a reliable blank.
As a practical rule, remove enough wood that the finished blank contains no pith and no visible crack connected to it.
Saving an extra inch of timber is rarely worthwhile if it causes the entire bowl to split later.
Does Every Piece Containing the Pith Crack?
No.
That is partly why advice on the subject can become confusing.
Some pieces containing the pith survive drying. A turner may produce a goblet, vase, ornament or small bowl with the centre included and experience no serious cracking.
They may then conclude that removing the pith is unnecessary.
But one successful piece does not remove the risk.
Whether the wood cracks depends on several factors, including:
The species of tree
The diameter of the log or branch
How quickly it dries
Whether the piece is turned thin
The orientation of the grain
Existing growth stress
Environmental humidity
Wall thickness
The final shape of the piece
Pure luck
A small branch with the pith running centrally through a thin spindle may behave very differently from a large bowl blank cut from the main trunk.
A thin green-turned form can also flex and distort as it dries, releasing some of the stress that might otherwise produce a major split.
The fact that some pieces survive does not make leaving the pith the safer method.
It only means failure is not guaranteed.
Can the Pith Stay in a Thin Green-Turned Bowl?
It can, but the design and orientation of the bowl matter.
A thin green-turned bowl is able to move as it dries. Instead of resisting all shrinkage, the walls can warp, ovalise and distort.
This movement may allow the piece to survive even when the pith is present.
However, the pith remains a weak and unpredictable area. Cracks can still begin there, particularly if one section is left thicker than another or if drying happens too quickly.
A bowl containing the pith is more likely to succeed when:
The walls are turned evenly and thinly
The piece is allowed to distort naturally
The pith is positioned deliberately
Sharp corners and heavy bases are avoided
The drying environment is controlled
Some cracking is acceptable within the design
Even then, there are no guarantees.
For a functional bowl that needs to remain stable, round and free from cracks, removing the pith is usually the better choice.
For a sculptural piece where movement and splits may add character, the calculation is different.
What About Hollow Forms?
Hollow forms are sometimes turned with the pith intentionally included.
The pith may be placed through the centre of the base, positioned on one side or used as part of a symmetrical end-grain design.
A thin-walled hollow form can move significantly as it dries, which may reduce some of the stress. The form may become oval or irregular rather than splitting apart.
However, hollow forms can also crack directly from the pith, especially where the base has been left too thick.
The base is often the slowest-drying and least flexible part of the form. If the walls are thin but the base remains heavy, stress can concentrate around the centre.
This is one reason experienced green-wood turners pay such close attention to consistent wall thickness.
Keeping the pith in a hollow form should be a deliberate design decision, not something that happens because the log was not processed carefully.
Can You Leave the Pith in Goblets and Spindle Work?
Small-diameter branches are often used for goblets, mushrooms, ornaments, handles and other spindle-turned pieces.
In this type of work, the pith may run along the centre of the finished object.
Sometimes it works perfectly well.
The smaller diameter reduces the amount of wood movement involved, and a thin stem or wall can flex as moisture leaves. The piece may distort slightly without developing a major crack.
But branch wood introduces other risks.
Branches contain reaction wood and internal stress because they supported their own weight while growing outward from the tree. The pith may also wander rather than remaining perfectly central.
A goblet made from a branch may crack, bend or move unpredictably even if it looked balanced while turning.
For quick green-wood projects, demonstrations and decorative pieces, the risk may be acceptable.
For something intended to remain precise or last indefinitely, straight-grained stock without the pith is more dependable.
What About Natural-Edge Bowls?
Natural-edge bowls are normally cut from half logs, with the bark forming the rim and the pith removed from the flat side of the blank.
This orientation provides attractive grain and a balanced pair of high points at the rim while avoiding the most unstable section of the tree.
There is rarely a good reason to retain the pith in a conventional natural-edge bowl blank.
Leaving it usually means cutting the blank too close to the centre line, increasing the risk of cracks through the base or lower wall.
The desire to maximise bowl depth can tempt a woodturner to include a little too much of the centre.
In practice, a slightly shallower sound bowl is more useful than a deeper one that splits during drying.
Can You Stabilise the Pith With Glue or Resin?
Thin cyanoacrylate glue, epoxy and resin can sometimes be used to fill or stabilise an existing crack.
They do not stop the surrounding wood from continuing to move.
If the timber is still wet, the crack may extend beyond the repaired area as drying continues. Another crack may form nearby, or the repair may separate from the wood.
Resin can be part of the final design, particularly in dry decorative work. It should not be treated as a substitute for removing unstable material during initial processing.
Trying to glue the pith back together is often a reaction to a problem that could have been avoided earlier with a chainsaw or bandsaw.
Is Heartwood More Likely to Crack Than Sapwood?
Heartwood and sapwood often dry differently, but the exact behaviour depends on the species.
Sapwood is the younger outer wood that transported water through the living tree. It commonly contains more moisture when freshly cut.
Heartwood is the older inner wood. It may be denser, darker and filled with natural extractives.
The main problem in a complete log is that different sections are drying, shrinking and responding at different rates while still locked together in a circular structure.
The pith lies at the centre of that structure.
Even where the heartwood itself is strong and attractive, keeping the complete centre of the tree enclosed gives the surrounding growth rings very little freedom to move.
Dividing the log releases much of that tension.
This is why processing the log promptly is far more important than simply coating the ends.
When Is Keeping the Pith Worth the Risk?
There are times when the pith may be kept intentionally.
You may want the growth rings to radiate symmetrically from the centre. The pith may form an important visual feature. The shape of the log may leave no alternative. You may also be willing to accept cracks, fill them later or incorporate them into the finished piece.
In those situations, keeping the pith becomes an artistic gamble.
That is different from claiming the risk does not exist.
A sensible approach is to ask what matters most for the particular piece.
If the goal is a stable functional bowl, remove the pith.
If the goal is a thin sculptural form and distortion is welcome, keeping it may be reasonable.
If the wood is rare and the grain around the centre is exceptional, the risk may be worth taking.
If it is a large valuable log that could produce several reliable blanks, risking the whole section to preserve the centre usually makes little sense.
Cracks Are Not Always Caused by Drying Too Quickly
When a blank cracks, the drying method is often blamed immediately.
The wood was left in too much heat.
It was not wrapped.
The end grain was not sealed properly.
It dried too quickly.
Any of these may contribute, but sometimes the problem began before the blank was ever stored.
If the pith was left inside, a crack may have been almost inevitable regardless of how carefully the piece was dried.
Drying methods can control moisture loss. They cannot completely overcome poor blank preparation.
Good drying starts with good cutting.
Process the Wood Before Trying to Preserve It
Freshly cut timber begins changing immediately.
The longer a whole log sits with the pith enclosed, the more opportunity there is for cracks to develop from the centre. Sealing the ends and promising to process it later may preserve the outside while damage continues internally.
Where possible, deal with the log promptly.
Cut it to manageable lengths.
Inspect the pith at both ends.
Split or saw the log through the centre.
Remove the pith and any existing cracks.
Shape the usable sections into blanks.
Only then should sealing and controlled drying become the priority.
This may feel wasteful when the centre contains attractive colour or grain, but removing unstable wood early normally saves far more timber than trying to preserve every possible inch.
Removing the pith is only one part of preparing fresh timber properly. How the log is cut, stored and dried will all affect how much usable wood survives.
You can find the wider process in my guide, Wood for Woodturning: Finding, Processing & Drying.
Final Thoughts
End-grain sealer can be useful, but it is not magic.
It slows moisture loss. It does not stop wood from shrinking. It does not remove growth stress, and it does not make the pith stable.
A complete log is trying to shrink around its own centre. As the heartwood, sapwood and growth rings move at different rates, cracks often begin at the pith and travel outward.
That is why I remove the pith when processing most logs for woodturning.
Some pieces containing it will survive. Thin green-turned bowls, goblets, hollow forms and artistic work may be worth the risk. But these should be treated as intentional exceptions.
For dependable blanks, the safest approach remains simple.
Cut the log open, remove the centre and seal the wood afterwards.
The best time to prevent a crack is before it has a chance to begin.
For more practical woodturning advice, tutorials and related articles, visit my Woodturning Guides & Articles page.
Thanks for Reading,
David
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About the Author
I’m David Condon, a woodturner and small business owner based in Tralee, Co. Kerry. I’ve been working with wood for most of my life at this stage — 11 years as a carpenter and over a decade running my own woodturning business.
Over the years, I’ve learned that woodturning is as much about patience and problem-solving as it is about tools and technique. I work mainly with Irish hardwoods, teach woodturning full-time, and spend most days learning something new in the workshop myself. On this site, I share the same practical knowledge I pass on to my students, shaped by experience, mistakes, and time spent at the lathe. If you’re interested in learning in person, I offer woodturning lessons in Tralee, with details available on my Woodturning Tuition page.
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More Woodturning Pages to Explore
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