Thread: Mango - yellow and black stains - from stickers??

I stickered around 3 cube of mango a few years back. I had to constantly restack the lot to avoid the staining. I was using both hoop pine sticks and ply sticks both stained. I selected a few choice pieces for personal use and the stains on a few were quite deep 5+mm, on others only surface. But it does get a "splalting" through it as I've only had a few pieces not display some staining internally.

This can be a problem with quite a few timbers. Best to use same specie stickers for known offenders.

So this black and yellow stain continues to be a problem.

I have tried scrubbing with Borax - nope, bleach - nope. I thought that perhaps exposure to light might improve it - nope.

Don't seem to be able to sand it out either. I noticed on one slab that as I keep getting deeper with the thicknesser the stain was getting worse.

Anybody have any ideas?

Brett, This is a common problem with light coloured timbers. The use of wet stickers will give trouble as will dark stickers on light timber if the stickers are not well seasoned. The safest method is to sticker with same specie and well dried. A more modern alternative is the use of plastic or poly type material for stickers.
None of this solves your current problem. There is every probability the stain will go down to about 5mm. In Mango it may be more as it is prone to stain.
Oxalic acid will often remove it, but not always. It very much depends on how severe the staining.

Thanks Ken. I scrubbed it with Borax this morning, and hosed it off soon after. It was quite a deep tannin colour in the scrubbing water but that just meant the whole surface was slightly paler despite heavy attention to the stripes.

How long does one leave the acid to soak in?

You did not mention the staining as being obvious when removing from the stack, only after thicknessing down, is this correct?

If so, it could be (I'm guessing) the additional pressure from the stickers has caused the timber to dry there slower thus allowing the bluestain to set in. Dry too fast and the slabs crack, too slow and the bluestain sets in.

These days on light timbers I spray/wash my slabs with a mix of boron and an antifungal to try an avoid bluestain. I have a stack of Doughwood (Melicope elleryana) slabs and blocks waiting for me to make some white tables. I know some of the larger carving blocks (up to 200mm thick) were fine on the surface but 1" down had the bluestain due to drying too slowly.

When you say you tried bleaching, with what? I've been playing around with concentrated pool chlorine (from pool shop) with water at 1:4 and soaking for up to a week. It is a risk though as sometimes it starts to break down the timber, making it spongy, so I check every 12 hours. Sometimes it turns the timber yellow, like Borax often does, but this disappears when dry again. This method only bleaches a few mm from the surface, i.e. whatever it soaks into.

Hmmm.... sounds like those slabs are destined to be cut up into turning blanks...

Originally Posted by FenceFurniture

Thanks Ken. I scrubbed it with Borax this morning, and hosed it off soon after. It was quite a deep tannin colour in the scrubbing water but that just meant the whole surface was slightly paler despite heavy attention to the stripes.

How long does one leave the acid to soak in?

If it is going to work, it will do so almost instantly. As you put the acid on, you should see the stains start to fade. Use plenty of acid..flood it on and rub in with a scrubbing brush. Usually a wait of about 10 - 15mins is enough for a satisfactory result. It very much depends how deep the stain is. If you have to leave it longer, so be it. There will be some bleaching on the surface , but that will be removed by the planer when the boards are dressed.
A long soak doesn't make it work better. Its a chemical reaction and if its going to work, it's pretty much instant.

Originally Posted by dai sensei

You did not mention the staining as being obvious when removing from the stack, only after thicknessing down, is this correct?

If so, it could be (I'm guessing) the additional pressure from the stickers has caused the timber to dry there slower thus allowing the bluestain to set in. Dry too fast and the slabs crack, too slow and the bluestain sets in.

The lines are visible straight out of the stack and don't seem to disappear when thicknessing in. There are other patches of black stain (and yellow) that appear to be not related to the stickers.

Originally Posted by dai sensei

When you say you tried bleaching, with what? I've been playing around with concentrated pool chlorine (from pool shop) with water at 1:4 and soaking for up to a week. It is a risk though as sometimes it starts to break down the timber, making it spongy, so I check every 12 hours. Sometimes it turns the timber yellow, like Borax often does, but this disappears when dry again. This method only bleaches a few mm from the surface, i.e. whatever it soaks into.

I used standard household "thick" bleach which is 5% Na Hypochlorite. I think I may have some pool chlorine down the back but won't be able to soak for more than 15-20 minutes until it starts drying up (no tank big enough).

Originally Posted by rustynail

If it is going to work, it will do so almost instantly. As you put the acid on, you should see the stains start to fade. Use plenty of acid..flood it on and rub in with a scrubbing brush. Usually a wait of about 10 - 15mins is enough for a satisfactory result. It very much depends how deep the stain is. If you have to leave it longer, so be it. There will be some bleaching on the surface , but that will be removed by the planer when the boards are dressed.
A long soak doesn't make it work better. Its a chemical reaction and if its going to work, it's pretty much instant.

That describes my process so I guess Borax is out. I used ¼ cup in about two litres of warm water. is that strong enough?

8 parts water 1 part oxalic acid crystal. Wash down well after bout 10-15 minutes. Carb Soda can be used as a neutralizer in the wash down if you are concerned about bleaching. The ratio for the soda is the same, 8 to 1.
Borax is not the answer.
I guess you are now finding out why there are some timbers I just don't like drying.

Originally Posted by FenceFurniture

.... I think I may have some pool chlorine down the back but won't be able to soak for more than 15-20 minutes until it starts drying up (no tank big enough).

wrap in a tarp to form a pool

Couple of pics after the treatments.

IMG_20190103_104240.jpg

IMG_20190103_104345.jpg

Have you tried Napisan or Wash-a-way (sp?) from Organoil? I’ve used both to remove tannins from Merbau and Tallow wood.