Green oak or should I say BLACK

[beganasatree]

Today I cut some green oak logs into boards with the chain saw,not very even so I put them through the p/t.The first 2 boards turned out great,the next one had some black marks on it after the first pass through the p/t and just got blacker with each pass.How can I stop this from happening,as I have a lot of logs to prepare .Can I treat the bed with something?? (hammer)

Peter.

 

[Beau]

Presuming the boards are wet as fresh cut. Wet oak reacts with iron and becomes black at the drop of hat. Sure someone will be along to explain the chemical process.

 

[Woodmonkey]

You're best off seasoning the boards for a year before you put them through your planer. Your planer will end up very rusty and you will have to plane then again once they've seasoned anyway. The black is the tannin in the oak reacting with the iron in the planer.

 

[yetloh]

Oxalic acid will remove the stain but I agree with Woodmonkey, plain it off when it has dried.

Jim

 

[Bm101]

Tannin can eat away at metal too if left for sufficient time if I remember some advice I was given years back by a green woodworker so it might be worth cleaning up your machine?

 

[Dan j]

Hi Peter.
A couple of coats of paste wax will help.
If you can wait, leave the wood out to dry for a few days or even a couple of weeks. Once the excess water in the surface of the wood has dried you should get fewer staining problems.
Dan

 

[ED65]

Tannin can eat away at metal too if left for sufficient time if I remember some advice I was given years back by a green woodworker so it might be worth cleaning up your machine?

Not sure about that, iron tannate is a very stable compound as shown by its protective effect inside iron tea kettles.

 

[Bm101]

Fair play Ed. Definitely not first hand experience. From memory he would have been talking about edge tools. Might it effect a sharp edge on tool steel if left uncleaned do you think?

 

[paulm]

Fair play Ed. Definitely not first hand experience. From memory he would have been talking about edge tools. Might it effect a sharp edge on tool steel if left uncleaned do you think?

I've found that it does on lathe tools, lathe bed, bandsaw table etc, although that was green sweet chestnut which has similarly high levels of tannin.

 

[wills-mill]

It's definitely a big issue with cast iron

You can set a length of waxed ply or MFC through the machine to stop bed/timber contact when thicknessing. You may still get problems if your final pressure roller is steel rather than rubber covered.

Some machines are set up to cope with green timber, I send a lot of green Chestnut and Oak through my Moretens/ Logosol ph260 four sider. It's built with nylon pads in the bed wherever there is a pressure roller, and the fences are anodised ali, so the timber comes out fine, even if the soggy chips are a bit clogging.

Weirdly, although the tannins seem corrosive initially, they do settle down and protect the metal. Fertan rust killer is tannin based, and the paintless bits on our sawmill stay a nice black colour as long as I cut Chestnut or Oak regularly. A few weeks on Douglas or Larch and the rust starts to make an appearance again....

 

[beganasatree]

Hi guys, thanks for all your replies. I am aware of the reaction between the tannin and metal. I just couldn't understand why the first two boards were fine and the third one started to stain. I suppose the first boards removed the wax from the bed allowing the next board to make contact with the bare metal. I did dry and rewax and oil every thing immediately after I finished. If I could chainsaw ln a straight line there would have been no need to use the thicknsser. The rest of the logs I will slice as best I can and stack lots of chainsaw practice, I might get some straight parallel cuts by the time I Finnish cutting. Once again I thank you for your replies.

PETER.