Do not do this....

I don’t know the exact science behind it but metal stains wood.

Well, I know that wet steal with stain oaks. Wet steel and iron filings use to used as a wood stain for that purpose. Looks like a similar process occurred here.

-- "At its best, life is completely unpredictable." - Christopher Walken

This also happens when black iron pipe clamps come into contact with the glue. There is a chemical reaction between the metal, glue and wood.

Oak is especially susceptible to this type of staining but it happens with other woods as well. Sometimes the staining is not very deep and can be sanded out, other times you aren’t as lucky.

Lew

Today I did make an experimental test on the effect of metal (steel) when in contact with wet wood.
I wet a piece of scrap wood with just plain water and another piece with glue and clamped both to my steel ruler.

I will let you know whether both have same or different results.

-- masrol, kuala lumpur, MY.

Here is the results :-

Looking at the pic above, the result is a bit surprising to me. The wood (top) was wet with glue and the other one (bottom) was wet with plain water. They were simultaneously clamped to the steel ruler for 4 hours.

-- masrol, kuala lumpur, MY.

Which piece got the numbers from the ruller?

The rule is stainless steel. It may be that there’s something in the glue besides water that reacts with the stainless steel.

-- Until you spread your wings, you'll have no idea how far you can walk.

Dave’s right…....... But very true….........do not get in a hurry. something always goes wrong when in a hurry.

-- Jerry--A man can never have enough tools or clamps

My assumption, water alone will not (as fast as glue or other chemical) cause steel to stain wood.
That’s why (maybe) finishers use to soak steel wool into vinegar-mixed water to make stain.

-- masrol, kuala lumpur, MY.

Try it with a piece of plain old cold rolled steel. Your rule is stainless steel. Different critter.

Steel wool is used due to the huge surface area. They are really after the iron in the steel.

In woods like oak it is the tannic acid that reacts with iron to create that black or bluish black staining.

-- Until you spread your wings, you'll have no idea how far you can walk.

Dave, do you think it is more like fungus rather than stain?
Rolled steel? Can I use my clean scrapper as an alternative? I supposed so..I will try

-- masrol, kuala lumpur, MY.

No. Not fungus. I think it is a reaction between the glue, or more properly, something in the glue and the iron in the stainless steel.

-- Until you spread your wings, you'll have no idea how far you can walk.

I’ve seen this reaction with wood many times both inside and out. Trees with “hardware” grown into them over the years perhaps from someone nailing a sign to a tree or a forgotten clothesline pully. I have found an old shotgun grown into the tree. The technical reason is soluble chlorides that are present in the wood can
form acidic conditions around steel in wet wood, and result in accelerated corrosion of the metal and weakening of the wood. Any one that has taken pallets apart to use the wood knows that sometimes those nails in contact with the wood are somewhat desintegrated leaving the immediate area stained. The wet glue has a similar reaction causing the metal to corrode and resulting in a stain the depending on the type of wood will travel within the porous cells as long as water and metal are in contact. As mentioned by others, oak has a lot of tannic acid and is extremely reactive with metal. There are also many different types of fungus that will cause staining (blue stain in pine and other softwoods) as well. Sorry for the long response but my wood chemistry is much better than my current woodworking skills. I lhope it answered some of your questions…

-- Allan

Marc, Chris Wright, Lew, Dave and Allan thank you for you time and participation in this forum, and also my thanks to all fellows LJs for viewing.
As suggested by Dave, I tried it with scraper card (non stainless steel) by wetting two pieces wood of the same species with glue and plain water to see wether they react differently when in contact with steel. I will post the result tomorrow.

Thank you everyone.

-- masrol, kuala lumpur, MY.

I’m pretty sure this should sand off relatively quickly. It ussually does when I get marks from my clamps.

Well, it looks like you’ve started the mineralize the wood with this technique. Another million years or two and you’ll have petrified wood, or maybe opalized?

-- "They who dream by day are cognizant of many things which escape those who dream only by night." ~ Edgar Allan Poe

HokieMojo, the answer is yes for the wood but if I were to sand the 1/32” thin veneer, I would have a bare frame.

-- masrol, kuala lumpur, MY.

good point. i didn’t think of how thin veneer can be.

I think I’ve heard that oxalic acid will remove iron stains in wood, effectively reversing the ebonizing that happens when tannins in the wood react with iron.