Teak turning grey while sanding

[chris95040]

Hello,

I've got some hefty pieces of varnished teak that were beautifully honey-colored, like you could eat them.

For various reasons unrelated to the finish it had to be taken down to bare wood (quick pass with a heat gun and sharp, flat blade scraper) and at this point it still looked nice and golden.

Now while sanding to prepare for a new finish I'm finding some spots are appearing to turn from gold to dark grey. Like, the opposite of what you imagine when sanding.

There's no caulk seam nearby that I'm pulling shmutz from, I've tried hand-sanding with a block instead of the RO, different grits, etc, but it keeps happening as i make my way through these pieces regardless.

I'm wondering if the wood is actually _deeply_ greyed in these sections and a previous owner "bleached" it before varnishing last time? This would explain an outer layer of honey colored teak followed by darker stuff underneath. If that's the case, perhaps I should do the same?

[coopec43]

Sorry, I can't help.

Are you sure the teak hasn't been coated with something like Sikkens Cetol?


Sikkens Cetol Marine Wood-Oil Varnish Natural Teak 946ml ...
www.whitworths.com.au › sikkens-cetol-marine-wood-oil-varnish-nat...
Sikkens Cetol Marine with Next Wave UV-absorbing technology is a protective, translucent and breathable wood finish for use above the waterline on interior and exterior woods. Suitable for all hardwoods, particularly teak. Wipe clean and recoat without sandin


Have you done some googling (or duckduckgo)?

"As the teak must be fully dry in order to sand it, you should leave it in a dry place for around twenty-four hours. Use only fine-grit sandpaper when sanding teak. Teak is a hardwood that reacts well to weather conditions. It has a fine grain, so sand in the direction that the grain is going.Jun 22, 2010"

How to Sand Teak Wood | DoItYourself.com

[Captn_Black]

Originally Posted by chris95040

Hello,

I've got some hefty pieces of varnished teak that were beautifully honey-colored, like you could eat them.

For various reasons unrelated to the finish it had to be taken down to bare wood (quick pass with a heat gun and sharp, flat blade scraper) and at this point it still looked nice and golden.

Now while sanding to prepare for a new finish I'm finding some spots are appearing to turn from gold to dark grey. Like, the opposite of what you imagine when sanding.

There's no caulk seam nearby that I'm pulling shmutz from, I've tried hand-sanding with a block instead of the RO, different grits, etc, but it keeps happening as i make my way through these pieces regardless.

I'm wondering if the wood is actually _deeply_ greyed in these sections and a previous owner "bleached" it before varnishing last time? This would explain an outer layer of honey colored teak followed by darker stuff underneath. If that's the case, perhaps I should do the same?

Try phosphoric acid (rust cleaner). Brings out the colour really well. A 50/50 mix should do the job.

[coopec43]

Anything here?



https://assets.cdn.thewebconsole.com...uide-small.pdf

[Captn_Black]

Originally Posted by coopec43

Anything here?



https://assets.cdn.thewebconsole.com...uide-small.pdf

There it says not to use phosphoric acid. But the bottle I have says that a 50/50 mix is good for teak. Could be based on marketing rather than science. Either way, you need a thorough rinsing with water after 15-20 minutes. I have used it with good results. Doesn't damage paint or sealants etc.

[danstanford]

The freshly sanded wood has lost the oil inherent in teak. Wait a bit and the oil will come back into the wood and give it the nice honey colour you expect. I vividly remember the first time I bought some very valuable teak for a customer and ran it through the planer....grey and ugly. To be honest I don't remember how long it took to bring back the colour but I bet in 24 hours you will see it most of the way back to a color you like.
Dan

[chris95040]

Originally Posted by danstanford

The freshly sanded wood has lost the oil inherent in teak. Wait a bit and the oil will come back into the wood and give it the nice honey colour you expect. I vividly remember the first time I bought some very valuable teak for a customer and ran it through the planer....grey and ugly. To be honest I don't remember how long it took to bring back the colour but I bet in 24 hours you will see it most of the way back to a color you like.
Dan

Interesting- I’ve sanded an awful lot of teak and haven’t encountered this, for example my ancient deck planks after being reworked sanded to a beautiful (albeit temporary) gold color.

I’ll try waiting a bit more but it’s already been 48 hours...

After reading more about these teak brightener products (never looked closely because old salts told me to stay away!) I’m starting to think my original theory is likely - this teak had its surface brightened before its last varnish job, and now I’m sanding through that brightened surface.

[Scaramanga F25]

Are you certain it is "teak". Many look likes in the industry.

[coolnige]

In support of Dan... I'm going with teak losing its oil when sanding. Heat from an orbital, belt or linear sander dries teak oil. It can look grey or brown and will need to sit exposed to air for even a week or two before cleaning and perhaps brightening prior to application of a coating. If sealed while grey, it will stay dull. Nige.

[Cheechako]

Maybe you used too much heat. Seems weird. I've never had teak grey from sanding heat.

[Sailor George]

Try Nu-Teak, it would great on my teak that had teak oil on it. Cleaned the teak with no sanding. Good Luck.