Thread: Mobilcer 195 or other sealant

Hi Bois - I'll kick off with my 2c worth:

"...how, where and when to use or not to use these end sealants."

Apply to all exposed end grain as soon after the tree is felled as possible. The idea is simply to limit the rapid loss of moisture from the vessels, allowing the ends to dry (& shrink!) rapidly compared with the rest of the wood, thus causing large end splits.

For a similar reason, you should at least split each log or billet down the middle. Water is lost more rapidly from the outside of the log, because a) obviously, it is closer to the air and b) it is still 'functional' tissue with medullary ray cells that can easily transport water radially. Further in, cells are dead & clogged with all sorts of gunk, so water can't get out easily. Worse, when the outside dries, it breaks any cappillary connection, so the inside water remains 'trapped'. Result is relatively rapid shrinkage of the 'sap' wood, but no movement in the heart, and the only way to relieve the consequent stress is for the sapwood to split.

You need to clearly understand the principles of these two processes to dry wood intelligently. I see lots of small pieces of wood like turning blanks, totally covered in wax. This virtually stops any moisture escaping, & certainly prevents cracking, so the bit looks perfect on the vendors shelves, however long it sits there. Then you take it home and expose the wood, on a good warm day, and suddenly, your lovely bit of exotica is full of nasty cracks. The number of times I've heard someone say "but it was drying for 2 years before I tried to work it..." You are going to wait a very long time if you expect any piece of wood to equilibrate with atmospheric moisture through a quarter inch of hard wax!

You also need to slow down moisture loss from sawn long-grain surfaces, to prevent surface checking (same principle as the raw log). This is particularly true of our Eucalypts, but any dense wood is at risk. Some softer and more compliant woods like Jacaranda rarely surface check, and can often be successfully dried 'in the round' because the heart wood is sufficiently compressible and the sapwood sufficiently elastic to absorb the strains of shrinking as the water leaves the cell walls.

There is still a lot of trial and error and a good deal of luck in drying timber well. Individual variation in trees is at least as great as it is with us, so what works with one tree in one place at a certain time of year may fail miserably over the hill on another day. Compression and reaction wood (laid down on the inside & outside of bends) are another problem - they can cause major cracking and scary scenes when you try to rip dried boards! Ensuring that moisture escapes more rapidly from the sides than the ends, & it all happens slow and steady is the best general recipe for successful air drying.


"...Do they breakdown?"
Depends what you use, but unlikely on the time scale required for effect. (I mostly use old water-based house paint, these days - it seems to work well.)

"... How often should they be applied? " Once should do it!

"...What happens if they are applied to other than the end grain?" See above.


"...Would they effect final applied finishes?"
Mostly it all gets sawn or planed off during stock preparation. Never been a worry for me.

"... Do they stop all moisture from leaving the green timber?"
Most don't, they simply slow it down, though several mm of paraffin wax must REALLY slow things down!

".. Do they stop any and all moisture from getting into the timber (say in a below ground situation)?"
Dunno for sure but doubt any of them are suitable for that sort of application - they are only surface treatments, after all, so if you wouldn't use paint for a job, you wouldn't use an end-sealer, either.

Cheers,

Well said! (But now what am I going to do with this soapbox? )

One minor thing: I check my blanks every now'n'again, checking their condition, and if I find a piece that has started checking I'll often give it another coat of Mobilcer. Leaving the cracks "open" is defeating the purpose of end-sealing...

If the splits gape wider than around 1mm wide or so (and no-one has 100% success ) I prefer to split the wood in two at the crack(s) and recoat, hoping to minimise my losses.

Too True, Skew!

I didn't mean to even suggest that I have anything like 100% success! But we can minimise the failures, with care. And accepting that two bits of wood just don't want to be together is a good policy, alright - cracks will happen, for explainable and uneplainable reasons.

Avagoodweekend,

Thank you sincerely for the excellent reply IanW.

Am still a little unsure about if you split the log down the middle you then have two separate sawn grain surfaces. Should these be coated for the full length? Or is it better to sacrifice the first board in order to allow the log to dry.

If water is lost more rapidly from the outside of the log (via the sapwood) then should the sapwood surface be covered in sealer?

I realise that if you were to do both of the above as well as the cut ends then the whole log would be sealed and I guess virtually no moisture would escape.

I wonder if it is possible to dilute the CER with something and apply different solutions to different areas and I guess to different types of timber according to how quickly or slowly it needs to dry out without splitting or checking.

Do you know if there has been any research done on this by Forestry or others, taking into account all of the factors that affect drying times, splitting and checking etc to produce an equation or rule of thumb that guides the effective use of sealants on green timbers.

I would appreciate your experience or intuitive guidance on the use of CER as I am heading out onto some large cattle stations in Central Western Queensland in June or July to cut a truckload of Budgeroo, Bulloak, Lancewood, Hairy Oak, Coolibah and a little Ooline (with a permit and already fallen), as well as a few other interesting species. I do not want to waste any of the timber we cut, not in terms of loss to ourselves, but as I believe that anything we cut down should be treated with the greatest respect.

And finally a question for yourself and Skew. Timbers like Lancewood can have a tendency to split from the cut ends very badly. I have seen some Lancewood that has split into five or six for nearly the whole length of the log from both ends, opening up two to three centimetres or more at the ends. The question is - would it make sense with these timbers or any timber in fact to band the ends in some way, with high tensile strapping, a wire cobb & co, or something else that would stop this cracking during the drying stage?

Thanks again. Regards Bois.

Originally Posted by Bois

Am still a little unsure about if you split the log down the middle you then have two separate sawn grain surfaces. Should these be coated for the full length? Or is it better to sacrifice the first board in order to allow the log to dry.

I don't know about "should" but I would.

If water is lost more rapidly from the outside of the log (via the sapwood) then should the sapwood surface be covered in sealer?

With trees that have easily removed bark (gums, etc.) I'll debark and seal all over. Others with tough bark I tend to ignore, although I do seal the ends of cut branches and the inevitable chain-saw mark where I'd rather one wasn't.

I realise that if you were to do both of the above as well as the cut ends then the whole log would be sealed and I guess virtually no moisture would escape.

End-sealer doesn't really seal the moisture in, it just limits the rate at which it can pass through; it doesn't really matter whether you use paraffin wax, Mobilcer, dilute PVA or house paint. The log will dry out over time. Totally sealing the log is the surest way to minimise splitting, but it also works out to be expensive in the long run. Hence I (and I think most others) tend to only apply it where it's going to make the most difference.

I wonder if it is possible to dilute the CER with something and apply different solutions to different areas and I guess to different types of timber according to how quickly or slowly it needs to dry out without splitting or checking.

I guess you could... Personally I wouldn't, but most of my logs can easily be replaced in case of disaster. My "precious" ones I just cover all over with Mobilcer.

Do you know if there has been any research done on this by Forestry or others, taking into account all of the factors that affect drying times, splitting and checking etc to produce an equation or rule of thumb that guides the effective use of sealants on green timbers.

Good question! I've no idea... somewhere here I've some PDF's on research done into kiln drying but I can't say I've ever come across anything on sealers.

And finally a question for yourself and Skew. Timbers like Lancewood can have a tendency to split from the cut ends very badly. I have seen some Lancewood that has split into five or six for nearly the whole length of the log from both ends, opening up two to three centimetres or more at the ends. The question is - would it make sense with these timbers or any timber in fact to band the ends in some way, with high tensile strapping, a wire cobb & co, or something else that would stop this cracking during the drying stage?

You'll find many fruitwoods are like that too. Cherry is a particular bug-bear of mine. I seal the ends as soon as I cut them, before I even make the next cut. Once I get the trailer home, as I unload I check each piece for splits and use any existing ones as guides to split down the pith. As often as not, I still end up with naught but pen-blanks by the time they're cured.

I don't know if there's any benefit to binding the ends... if you decide to try it don't forget to post the results every now'n'again.

Lancewood is a bugger to dry, for the very reason you mentioned. Unfortunately I've only ever had failures so if you find a way, please tell.

However.... once the Lancewood has split, you have 1/4 split pieces to work with which are remarkably stable.
So the splitting is good news, you just have to accept that characteristic and give up the desire to get through and through slabs.

Most Lancewood is pretty small stuff now, if you get some larger trunks - lucky you!

Thanks Skew and Clinton. A great help .

I will treat about twenty logs as experiments and keep accurate records of times (till treatment), sizes, amounts and position of treatments, moisture levels, drying times, final results and problems (and anything else suggested as important) and report these back over time.

Thanks again. Regards Bois.

What's your plan with all that beautiful timber? For yourself, or to sell? Your timber list certainly interests me.

I was thinking of planning such a trip myself as short holiday of sorts to use up my excess leave. Camping under the stars, travelling at leasure, and scoring timber - perfect cheap holiday.

yes, dai sensei has raised a good point.... i.e. can I get me hands on some of your timber!
Seriously? I'll have some chisels to put handles to soon

Good luck with it, and will be interested in your thoughts on the drying.

Hi Dai Sensai & Clinton,

I am investigating if it is viable to set up a business supplying only Australian species with a particular emphasis on some of the extraordinary timbers of Western and Central Western Qld. I lived out there on cattle stations for 25 years and saw the incredible waste of this valuable resource through millions of hectares of land clearing for pasture and crops.

This will be a trial run to cut and or collect a semi trailer load of timber with the majority being Budgeroo, but also some other species where they are abundant and we can selectively harvest with minimal harm to the environment. We will take recently fallen or pulled timber as well as rung or tordoned timber and use coppiceing where we can.

We will go out for about two weeks and camp out in one of the most rugged and fascinating areas in Australia. Collecting the timber will take about five days and the rest of the time we will explore the area and look towards the next load if it works out.

We hope to sell some of the timber to cover the costs of the trip but we also hope to be able to give a proportion of the timber to woodworkers who can use it in a utilitarian or creative way with an agreement that we may photograph the end results and use these photographs for display or marketing purposes.

And yes, for us, camping out under millions of stars, cooking in a camp oven or bedourie and sitting, staring into the campfire at night, while in the middle of the outback are indescribable life-enhancing experiences.

Regards, Bois

Sounds like a great idea. Let me know if you need someone to help out in exchange for some of that timber.

Originally Posted by dai sensei

Sounds like a great idea. Let me know if you need someone to help out in exchange for some of that timber.

Hi Dai Sensei, Yes, a possibility. Still planning, costing, organising. Thinking of going June at earliest or August at latest. Perhaps should meet sometime and discuss the idea and the trip. Will keep in touch. Am sometimes away from the computer for days at end but will always get back.
Regards Bois

hi
just a really quick question, when they say that wood seasons approximately 1 inch per year, is that from the end grain or is that from all surfaces of the wood? for instance, hypothetically speaking, were i to have an unseasoned stick with a diameter if 1 inch but was 4 inches long, would it take 1 year to season in from all faces of the stick or would it take 4 years to season inwards from each of the end grains?
oh, and another quick question, does anyone know of a chart or table which lists a large number of wood types and suggests whether they are likely or unlikely to split during the seasoning process and if extra measures should be put in place to avoid this?
thanks
jim

I've always taken it to mean the cross-grain thickness, not "length of the grain."

It's only a "rule of thumb" though... a quick but rough guesstimate.

eg. I'd expect your 4"x1"x1" blank to dry in 6-9 months, but if I cut a 6 foot long 6"x1" plank from a green log, I'd expect it to cure within a year or two.

If you're planning on drying timber on more than a minor scale, it's a seriously good idea to spend the pennies and buy a good quality Moisture Meter...