Thread: Sauno kiln

Originally Posted by TasSculptor

I just got a Sauno kiln unit from logosol and will be building the insulated cabinet and setting it all up shortly. Im looking forward to testing it out on various types of timber. It steams the wood first and then dries and the manual says you can put green timber in it. Apparently Red oak (an American species I think) has to be air dried for at least 6 months beforehand because it contains corrosive Tannic acid which can wreck the heater/blower unit and I was wondering if the same might apply to Blackwood or other species. Any ideas? Any tips etc. would be appreciated.
Regards. Jason.

All eucalypts contain Tannic acid especially in the leaves and bark and some also contain a lot in the wood. This is the main reason why most milling equipment turns black and why many Australian creeks and rivers are brown.

Ironically (Har Har) while it does corrode the steel, tannic acid is also a (very expensive) rust converter as the tannic acid in the sawdust reacts with the rust forming Ferrous Tannate.
In fact when we bought a used bandsaw mill I deliberately sprayed tannic acid onto rust parts of the mill to prevent rust from developing further.
see BobL throws the Chain Saw Mill in for a bandsaw mill!
This is way some museums preserve ancient rusty iron artefacts so I followed this up and now make my own Tannic acid brew to uses as a rust converter.
Restoring Metal objects and surfaces
Unfortunately the ferrous tannate covering is not very robust and will flake off so it needs covering with some sort of top coat like a paint.

I suspect the problem is the steaming process as it will extract large amounts of tannic acid from the wood and when combined with all the water from the steam you will end up with an acidic soup and thats what will attack the blower.

The timbers that I mill that stand out as having lot of tannic acid are Spotted Gum and WA Tuart as they turn steel black almost instantaneously. Spotted gum retains a lot of tannin even when it is dry and can be seen on WW gear and tools while working it.

I recommend you do some research before you ruin your nice new Sauno.

I would be interested to know the volume and running cost for the kiln.

Thanks Bob. I will err on the side of caution and let the timber sit for 6 months or so I reckon.

Six months air dry is always a good idea with eucalypts before kiln drying.

TasScultor, can you start a thread on your build and how the drying process goes?

I read the manual and I get a LOT of local timbers... Id LOVE to turn these into usable items ASAP. Its very appealing. http://www.logosol.com.au/downloads/...iln_manual.pdf

AS Bob says, all Eucalypts have tannins aplenty. Most acaccias too!

I think from my read of the manual the issue lies in the tannic acid reacting with the polystyrene chamber. To avoid that my thought would be to not use a polysterene chamber, or line the chamber to protect it perhaps? Ours chamber is built of bitumen coated ply on frame - with closed cell foam in the wall cavity (MUST use closed cell foam in a kiln or it'll only last 12 months before it rots BTW, and dont let some foam salesman tell ya that open cell will work, unless hes giving you a three year warranty on it). We've got an R value of about 9, but this is the tropics. And insulate the floor exceedingly well.

I'm going to follow this along quite closely - I've often eyed off the Sauno units because there are times when a little kiln to do odd jobs would be handy. The only issue I see is that with the recommended process I suspect you'll burn near as much power on a load as we do for a lot less charge. Takes a bit of juice to bring a load of timber up to 70 degrees and hold it there for a few days... our low temp DH unit runs at about 48 degrees tops, and the way I read the Sauno manual about the time you stop steaming and start drying we're just about cooked.



Edit: So I had a bit of a look around at the literature this morning (rainy day, Sunday, and I'm stalling go to work). Basicly its a scaled down low temp conventional kiln. In effect, its a 4000w electric heater and a small fan, stuck inside an insulated box. Running costs look like around $50 AUD per cube in direct (electricity) costs, plus you'll need to factor in the dollar value of loading and unloading the charge of timber, depreciation etc etc. Compared with high temp conventionals your direct costs are cheap, but your cycle time is way longer, looks like about a month for a charge of around 1m3. That's a cost of a different sort.

So we load it, toss a couple of buckets of water on the floor, shut the door and turn it on. It's only a baby unit so it takes a while to come up to working temperature of 70 celcius - its not like heating a (basicly empty) house room with a 4000w heater, we actually have to lift the temperature of the contents of the room chamber to that temperature too and with wood that takes a while, wood is a most excellent insulator. The water on the floor is to allow the relative humidity to increase as well, the higher the RH the (a) more heat the air can carry and (b) wet wood is easier to heat then dry wood and you also get some (c) softening of the lignin which allows the moisture to travel through it easier. (c) will allow your air dried timber to equalise itself, removing the moisture gradient between shell and core.
After about 6 days we come back, drop the thermostat back to run temp, open the floor drain to vent any excess moisture from our buckets of water, crack the exhaust vents open and away she goes... now we're actually drying. And being small it takes three weeks. Dry external air is sucked into the chamber, circulates through the stack picking up both heat and moisture, and gets vented out to be replaced by more dry external air.

I've got no doubts it'll work, though I am not impressed with the actual chamber. I think you need to over-engineer somewhat compared to the supplied plan. Kilns get loaded with wood, wood is harder then styrene, and if your loading with a forklift then it'll be really easy to deconstruct the chamber with a pack of timber. I don't like the door system either... it requires too much care when loading. Honestly, for the size of the chamber, look at having the whole top lift off the floor section with the forks, or a block and tackle mounted over it. Particularly if you havent got forks hand loading in a chamber where you cant really stand up is going to be hard work. Looking at the size of the thing the floor/ walls joint is about the same size as the side panel anyway. All you need is a skirt of "pinch weld" rubber gasket on either the bottom of the chamber or the floor and she'll take up as tight as the door will. If going that way its probably a smart move to put a little man door into the end wall, do that anyway. You dont want to be opening a main door to make a check on progress; the heat lost doing so has to be built up again and that takes more time and more electricity.

Buy a good moisture meter with a remote probe, that way you can read moisture levels without opening the door at all. And I would suggest if you are going to try and dry from green at some point that you invest in a wet and dry bulb thermometer set... the directions supplied will kill wet timber, drying timber from green is an unforgiving process that requires very careful moderation of temp and wet bulb depression to achieve any form of satisfactory result.

I think you'll be fine with it. Production is limited but so is the price: I think if you can live with the production constraints then you'd be mad not to have one. A kiln - even a small one - is a money making machine for any professional sawmiller playing with cabinet/joinery species. Forget the increase in value because its now KD, that isnt as big when you factor in the costs as it appears. The real money is in market acceptance and ROI : that last lot of logs you bought that can now go to market in 7 months (6 months air drying and one in the kiln) not a couple of years, and being able to convert dollars invested in logs and milling costs back into dollars received from sales in months not years is a total game changer.

Hi. Anthony from Logosol (Australia) here.

It’s good to see a discussion about our Sauno kiln units and thought I’d add a quick message to mention I’m happy to contribute any information I can.

A little background… my company (Ideal Tools) took over the Logosol distribution in Australia only last year and feedback as to how people were going with their Sauno kilns was very limited. So I thought we would take a fresh look at the Sauno kilns and begin to build up some data on their use in Australia and on our local timbers.

First up I have set up a kiln for testing and will get it operational shortly as soon as I get a suitable data logger gear to record temp, humidity, ambient temperature; and importantly, power consumption.

I hope to feedback this information so people can make informed decisions on getting and setting up one of our Sauno kilns.

Some interesting discussion below on the Tannic Acid, so we will add that to the mix of information we gather as well. Especially any impact on Kiln longevity.

One thing I would say at this point, although we have a Styrofoam kit available, we strongly recommend people build their own insulated enclosures to suit their needs and budgets. Used refrigeration panels would be excellent. We have plans available for fitting out insulated containers with Sauno Kilns.

I don’t want to swamp this or any other threads with too much manufacturer input, but thought I’d mention I’m here to provide any information if requested, and take on board any feedback.

TasSculptor – I hope you get your Sauno kiln operational soon and let us know how it goes.

Well I finally got the kiln built! I get sidetracked easily.... Anyway, I went with a lift off chamber as JohnG suggested for ease of loading and a few other tweaks here and there. I cut a good stack of Sassafras and Musk to try it out, both prone to checking and I'm drying from green. I only saw johng's edit re. drying from green just now so if he sees this some more tips will be much appreciated. I will be loading it tomorrow and firing it up. Very exciting. If my construction holds up for the full cycle I will report back in a month or so with some pics of the kiln and hopefully some nice dry wood with very little checking!

Without pictures it hasn't happened, you know that right?

ummmmmm... do a google search for "Dry Kiln Operators Manual" Its a USDA forestry book and you'll be able to download a free PDF copy online. In the back of it theres a section on schedules, including Australian and Oceanic Species. Hopefully they've got a published schedule for Sassafras or Musk, if not pick something similar from the list. If they do have a schedule for both then pick your schedule to suit the harder one to dry. The schedule listed (say T2-C3) will relate to a table further back in the book
The table will give you wet and dry bulb settings to aim for and tell you what moisture level you need to change the wet/dry bulb settings at. Schedules are reasonably conservative so its not like you need to be up at 2am to change a setpoint.
Elsewhere in the book theres a section on converting the published schedules (which were written for conventional kilns) to low temp and DH kilns. Basicly what to ignore because we cant get that hot anyway so do this...

Thing being of course that I dont know if you can control that kiln to that degree, or if having wet and dry bulb temps and moisture levels would mean that you know whats happening and cant do a dammed thing about it. Guess we'll find out. And if its as slow as I think it'll be then its probably not an issue anyway... slow is safe when we're drying wood so long as we arent trying to avoid some type of fungal staining issue like with pine.

This is why I always try and air dry a bit first. If you can get it below 20% MC before it goes in the kiln you can pretty much open a low temp kiln up and run it hard. Its the high MC levels that require the watching and set point changes to prevent checking problems. Anything above 20% MC is free water not bound water (in the wood) so it runs out reasonably fast - couple of weeks - when air drying. Also my inner tightarse hates paying for power to do what a month in the shed would achieve naturally anyway.

Have fun, lotsa pictures please.

Also started cutting some brown sal last week. I'll get that bit I promised down to you soon as shes cooked. Allow a couple of weeks for air drying LOL.

Wet wood should have an air dry first, particularly as we get into warmer weather. Dropping the free water out of the timber prior to kiln makes for more even drying and much less downgrade. It also speeds up the drying process without creating an aggressive atmosphere in the kiln.

It has begun...

So what's the panel material? Curious minds - well me at least - want to know.

Y know, after a few loads, some of which will probably be less then perfect because it's learning curve stuff... well one day you start feeling comfortable with running it and you don't fret too much about the entire operation. And then comes the brilliant lightbulb moment when you realize that after you go home, in fact pretty much all day everyday... it's sitting there working away making you money. Not a lot of machines in a sawmill will do that without someone there to drive them!

Originally Posted by John.G

So what's the panel material? Curious minds - well me at least - want to know.

Y know, after a few loads, some of which will probably be less then perfect because it's learning curve stuff... well one day you start feeling comfortable with running it and you don't fret too much about the entire operation. And then comes the brilliant lightbulb moment when you realize that after you go home, in fact pretty much all day everyday... it's sitting there working away making you money. Not a lot of machines in a sawmill will do that without someone there to drive them!

The panels are 50mm extruded polystyrene insulation panels, its the closest I could find to what was specified. They are quite dense and seem fairly sturdy.... time will tell.

DING DING DING!!! (That was your oven timer. )

How'd it go? Good/bad/ugly??? Nothing wrong with any of the above results... (well its not good if its bad but anyone whos never ruined a kiln load of timber has never run a kiln) and I've been wondering how you got on for the last week.

Originally Posted by John.G

DING DING DING!!! (That was your oven timer. )

How'd it go? Good/bad/ugly??? Nothing wrong with any of the above results... (well its not good if its bad but anyone whos never ruined a kiln load of timber has never run a kiln) and I've been wondering how you got on for the last week.

Haha. Bad to ugly...... bit disappointed but will be trying another load in the next month or so with a few adjustments and what not.