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Reply by Craigils

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Posted on How to finish this Cottonwood/Poplar

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Craigils

3 posts in 96 days


#1 posted 01-06-2021 10:27 PM

#1) Species:
One pic makes any comment on species a guess? :-)

Thank you for your information regarding the different types of trees.
I have discovered that this is likely Populus Canescens, a South African Poplar plant. Called Cottonwood due to its cottony texture.

#2) Crack:
Check moisture content. If less than 10-12%, then stabilize it, or cut it off as needed. Need to stablize cracks in slabs is normal due thickness and internal stress of tree.
If need full length of slab, need to stabilize the crack with bow tie insert, slow cure epoxy, or both. Otherwise, cut off the crack, making sure there is not cracked beyond the open portion.
If slab is more than 12% moisture, the crack might grow as it dries further. Then need to seal ends, and wait many months for it dry out and stop moving before dealing with crack(s).

Thanks very much for this. I didn’t know about methods of measuring wood moisture. My search results say I can either use an oven to dry a piece out and compare weights, or use a moisture testing tool. Using a tool seems much easier, and it looks like they can be as cheap as R300 (about 20 USD). Am I likely looking at a bad tool not good enough for the job? Or would this be fine?
https://www.builders.co.za/Tools-%26-Protective-Wear/Measuring-%26-Marking-Tools/Electronic-Measuring-Tools/Ryobi-Moisture-Meter/p/000000000000700855

To be honest, since I bought the wood from a reputable wood company, I expect that it has been sufficiently dried. Or can I not take that for granted?

Lastly, if the moisture content is still high, and I cut the cracked part off, will it just continue to crack anyway? So there’s no way to stop the crack if the wood does still have too much moisture.

#3) Finish:
Pick one you like. Solvent base has advantages, so does water base. Neither one is better or worse for large thick slabs. Only suggestion is finish both sides to ensure even movement as humidity changes during use.

Thanks for the advice about finishing both sides. Very valuable to know. And thanks for assuring me that there’s no right or wrong answer with oil vs water base

#4) Stain:
Difficult to stain or blotch prone woods make adding color more difficult. Cottonwood tends to have stringy/fuzzy grain and can be challenge to sand smooth and stain evenly. Yellow popular will botch, but is easier to finish with blotch control.
There is no difference between lumber and/or slab regarding use of stain? Personally, I think large slabs are best left natural with clear finish. If wood color is not a match your home these, then pick another slab and let beauty of wood show.

I think youre right about leaving the slab to keep its natural colour. I got caught up in all of the info about the challenges of staining and forgot about the option of just leaving it with its natural beauty.

Is there anything more to clear coating other than just the clear coat? Should I be pre-coating it with something before the clear coat? Or putting anything on top of the clear coat?
I’ll probably be using something like this
https://www.fired-earth.co.za/wood-works


Why do new woodworkers always want to stain. It’s such a difficult path to start on.
The board doesn’t look like poplar to me.
- Aj2

You’re right. As mentioned above, I have decided to keep it simple and not stain the wood


The OP is talking about wood from South Africa. I think it is like our cottonwood.

- Russell Hayes

You’re correct. I have since discovered that this is Populus Canescens, a South African derivative of the Poplar tree


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