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I bought a 210×65×3.8 cm oak countertop and attached metal legs to it to make a desk. It was unfinished, so I sanded it and applied 3 coats of shellac to the top and edges (with a light sanding after the second coat). Following Is it necessary to apply finish to both sides of a table top?, I did not finish the bottom. I also did not fill the pores before applying shellac.

Now that a month or so has passed, I am noticing small cracks here and there along the pores. These cracks definitely were not there initially, and it seems that they appeared gradually over time. They exist on both sides, although it seems the bottom (unfinished) side has more of them.

Some pictures:

Top side

top side 1

top side 2

Bottom side

bottom side 1

bottom side 2

My questions are:

  1. Have I done anything wrong?
  2. Will my desk eventually crack and collapse?
  3. Can and should I do anything about this? (E.g. fill the cracks with glue, finish the underside.)

Appreciate any help!

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  • Hi, welcome to StachExchange. Are the cracks all new or have you just had the opportunity to notice them as you've spent time with the panel? Re. your numbered points, 1, no. 2, no, this type of construction is inherently stable due to each potential weak point being surrounded with lots of strength. 3, depends on whether you want to + if the cracks are all new, or were there initially. Now, how do you intend to use your desk? Shellac would not normally be enough protection for a piece of modern, everyday use furniture, but it depends on use type and amount, and your tolerance for stains etc.
    – Graphus
    Mar 28, 2021 at 17:15
  • Also wanted to add (and this is just a personal bugbear, not of vital importance) this is not butcher block. It is becoming increasingly common that it is described that way but butcher-block construction is glueing pieces together so that the end grain is uppermost... as in actual butcher's blocks. In the UK/Ireland this method is sometimes described as 'stave construction'. Unfortunately there doesn't appear to be a better term for a glued-up panel like this in American parlance.
    – Graphus
    Mar 28, 2021 at 17:20
  • Thanks @Graphus! Noted regarding butcher block!
    – stanch
    Mar 28, 2021 at 18:16
  • @Graphus The cracks definitely appeared over time — they were not there while I was sanding and finishing. Although it is hard to say how soon they appeared. I would say at least a couple of weeks passed before I noticed the ones on the top, but they are few. I have a feeling the ones at the bottom have been multiplying but only today I marked them so that I can track this in the future. I don’t mind the cracks from the aesthetic point of view (at least definitely not the ones on the underside), my only concern is the stability of the desk.
    – stanch
    Mar 28, 2021 at 18:19
  • @Graphus Regarding desk usage, I am being very careful. On the rare occasions I eat or drink I use coasters. I also have barely any things I move around on the surface. I bought shellac in flakes rather than pre-mixed so that I can refinish as needed down the line.
    – stanch
    Mar 28, 2021 at 18:23

1 Answer 1

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  1. Have I done anything wrong?

Not that I can see. The simple truth is that a commercial product made from kiln-dried wood should basically never exhibit cracks after it is installed in its final destination, even if left for an extended period of time with no finish on it1.

  1. Will my desk eventually crack and collapse?

I doubt complete failure is possible with stave construction, but it's impossible to predict what's going to happen in the short and medium term.

You'll have to monitor and see if the problem progresses, or if the wood has settled down and done all the cracking it's going to. As mentioned in the Comments, I was going to suggest marking both the location and the extent of all the cracks on the underside. That way you'll know for sure if A) new cracks form and B) if the existing cracks get longer. In either case alarm bells should sound.

There are some who would say you should enquire about returning this now. I would at least investigate the possibility, explaining to the vendor what has happened and see what they say; they should NOT tell you that a few small cracks (of this kind) are normal! They aren't. I've seen dozens and dozens of examples of this type of glued-up panel in beech and birch (hello Ikea) and in oak (other furniture, kitchen countertops) that have no post-finishing cracks that I could see. Ergo I don't think it's a matter of opinion that these are not normal or to be expected, and that more than a few pieces of the wood used in the construction were flawed in some way2.

If more cracks appear and/or the existing cracks continue to grow then I think asking for a replacement or refund is definitely the right call.

  1. Can and should I do anything about this? (E.g. fill the cracks with glue, finish the underside.)

Assuming the wood is done cracking, you can probably safely live with any of the cracks that don't bother you, especially the ones on the underside.

Most of these cracks appear superficial but even more major cracks in one or two of the staves should not be structurally significant because of the method of construction, where the affected pieces are surrounded by strong glue joints and other pieces that are stable.

If you did want to fill the cracks on the top, you have various options but note that anything that involves glue will pretty much guarantee you'll need to refinish the top3.

I won't cover the how-to aspect of filling but will quickly list all the fillers that I think are currently available:

  • Wax filler — various kinds, softer types are basically like crayons but a better option for a working surface is one of the harder types that need to be melted in.
  • Shellac filler. These are much harder that almost all wax fillers, and also need to be melted in.
  • Glue + wood dust — the ideal glue for this not being PVA glues.
  • Superglue and sanding dust. I mention this separately because you don't normally mix the filler and then apply it because of the very fast setting time of superglue.
  • Shellac + wood dust. This takes a surprisingly long time to dry hard but can make for nearly invisible fills of fine cracks and gaps in joinery that will subsequently be finished in the same shellac.
  • Straight epoxy (high on my list as the best option).
  • Commercial wood fillers.

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1 Something that is actually extremely common in commercial kitchen installations for example, where the panel may arrive on site days at least before installation, and after the install the counters may sit unfinished for weeks, and sometimes far longer. Also worth bearing in mind that the bulk of such installations are to houses where building is still in progress — with plaster still drying, and no heating.... so the short time you had it on your terrace should have zero bearing on this.

2 I suspect improper drying — possibly left too wet (so the wood is now drying and shrinking), or dried too quickly (leading to defects). The last image in particular, those appear to be 'surface checks', which the textbooks tell us are a drying defect.

3 Since you used shellac which is very repairable you might think you wouldn't need to do the whole top, and in theory small repairs can be done and seamlessly blended in. But it's best practice not to locally sand small areas of a large flat surface (because making shallow depressions are virtually inevitable). This will lead to a slight, but perceptible, waviness that you may be able to feel, but will surely be able to see in raking light or when light is reflected from the polished surface.

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  • I've definitely seen cheap oak countertop surfaces like this (it's called Leimholz in Germany) do this. I assume it's because of corners cut in the manufacturing. Here we have several grades, and the "rustic" grade has a lot more sapwood - it looks a lot like those pictures.
    – colinmarc
    Mar 31, 2021 at 20:13
  • @colinmarc, thanks for that. Here the most common exposure to this material is mass-produced solid-wood furniture, the most infamous vendor being Oak Furnitureland which gets a lot of (deserved) criticism. But still, post-finishing cracks are rare from what I've seen.
    – Graphus
    Apr 1, 2021 at 16:08

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