Larry Moore Posted September 6, 2015 Report Share Posted September 6, 2015 I am finishing a cherry shelf unit and after sanding and applying a waterborne blotch control I have green specks and some green areas on most of the shelf pieces.They are not big enough to show up in a picture but they are clearly visible to the eye. I suspect a reaction between the sandpaper substrate but I'm not sure. I do not know what the paper is, it was some given to me by 3M 20 years ago.Does my suspicion sound right? Quote Link to comment Share on other sites More sharing options...
Keggers Posted September 6, 2015 Report Share Posted September 6, 2015 Could well be the case. Did you vacuum the surface prior to applying the blotch control? A very light sanding - which you'll have to do anyway - followed by a good vacuuming might take care of the problem. Quote Link to comment Share on other sites More sharing options...
Trip Posted September 6, 2015 Report Share Posted September 6, 2015 You know, I’ve seen this... But for the life of me, I can’t remember where or the circumstances... It’ll come to me, but probably after your project has been completed for a year or two... It’ll dive me crazy until I remember where...I’m not sure it’s the sandpaper – even old sandpaper... Unless you stored it loose in a steel drawer for 30 years...So if I understand your workflow: all you did was sand, apply some blotch control, let it dry and you got some green specs? The part about vacuuming is important... Anything else? – maybe steel wool for the corners? And nothing old-school – like metal acid dyes to pre-darken the Cherry?We could play chemist and neutralize... Or you could sand-back...Do you have enough scrap to experiment a bit?Who’s blotch control? Did you use it straight, or dilute it?Now I remember – it was a Cherry AV rack with a lot of spalting... Really nice Pens Black... I think we used CN’s blotch control and a WB dye schedule... Now I just have to remember what caused it... And more importantly, how we fixed it... Let me noodle on this a bit... Quote Link to comment Share on other sites More sharing options...
Larry Moore Posted September 6, 2015 Author Report Share Posted September 6, 2015 (edited) No vacuum, just a wipe downIn the back of my mind I think there was some sandpaper mediums that did not like water. The age reference was more cause I can't remember back that far to know what it is. It is CN blotch control applied straight with no dyes or steel wool.I still have probably 50bf left so yes I can and will go out and see if I can recreate the problem Edited September 6, 2015 by Larry Moore Quote Link to comment Share on other sites More sharing options...
Tpt life Posted September 6, 2015 Report Share Posted September 6, 2015 Green makes me suspect copper oxidation. Bronze or copper on your tools? Quote Link to comment Share on other sites More sharing options...
Larry Moore Posted September 6, 2015 Author Report Share Posted September 6, 2015 Green makes me suspect copper oxidation. Bronze or copper on your tools?nope Quote Link to comment Share on other sites More sharing options...
Boatworks Today Posted September 6, 2015 Report Share Posted September 6, 2015 Here's my guess. Sandpaper comes in a couple varieties; stearated and non-stearated. Old stearated paper was coated with zinc to help prevent clogging. Newer versions use something other than zinc so there's less chance of an issue with modern finishes. But, I've worked with finishes that specifically state to use non-stearated paper. I suspect if you're getting green specs it's due to a reaction of bits of paper containing zinc being stuck in the pores of the wood and reacting with the WB finish. Just spit-balling though! Quote Link to comment Share on other sites More sharing options...
Larry Moore Posted September 6, 2015 Author Report Share Posted September 6, 2015 Here's my guess. Sandpaper comes in a couple varieties; stearated and non-stearated. Old stearated paper was coated with zinc to help prevent clogging. Newer versions use something other than zinc so there's less chance of an issue with modern finishes. But, I've worked with finishes that specifically state to use non-stearated paper. I suspect if you're getting green specs it's due to a reaction of bits of paper containing zinc being stuck in the pores of the wood and reacting with the WB finish. Just spit-balling though!that's what is stuck in my head too Quote Link to comment Share on other sites More sharing options...
Trip Posted September 6, 2015 Report Share Posted September 6, 2015 Zinc in the paper... Interesting. Before my time... Learn something new every day...Well, you could take an off-cut and prep it with the sandpaper you've got on one side and some new stuff on the other. Apply the blotch control and see what happens... I emailed the guy I worked the 'green blotch' project with to see if he remembers what went wrong... Quote Link to comment Share on other sites More sharing options...
Tpt life Posted September 6, 2015 Report Share Posted September 6, 2015 (edited) Would love to know what makes the Zinc green. I have worked with a lot in many applications and have not seen green. Reading lots with regards to chromate vs sulfate. Edited September 6, 2015 by C Shaffer Quote Link to comment Share on other sites More sharing options...
Trip Posted September 7, 2015 Report Share Posted September 7, 2015 Would be worth eMailing CN to get his input. If something makes his product show green, then I bet he'd know what it would be... Quote Link to comment Share on other sites More sharing options...
Boatworks Today Posted September 7, 2015 Report Share Posted September 7, 2015 Would love to know what makes the Zinc green. I have worked with a lot in many applications and have not seen green. Reading lots with regards to chromate vs sulfate. Like I said, just spit-balling ;-). Seems there's some sort of reaction going on, so far the paper is the only variable I can see.. Quote Link to comment Share on other sites More sharing options...
Tpt life Posted September 7, 2015 Report Share Posted September 7, 2015 Not arguing, learning something new. Quote Link to comment Share on other sites More sharing options...
Trip Posted September 7, 2015 Report Share Posted September 7, 2015 (edited) Well, maybe Larry hates finishing, but learning something new every day is what I love woodworking... Edited September 7, 2015 by hhh 1 Quote Link to comment Share on other sites More sharing options...
Larry Moore Posted September 7, 2015 Author Report Share Posted September 7, 2015 I went out and found the off cut from one of the shelves (24"). I sanded half with the same paper and applied CN to it. I did think of another potential culprit. I used blue paper towels to apply the CN, so I used those on part and a cotton rag on part. I will see what it looks like in the morning. Quote Link to comment Share on other sites More sharing options...
Trip Posted September 7, 2015 Report Share Posted September 7, 2015 Looking forward to the results... I love this sh*t... 1 Quote Link to comment Share on other sites More sharing options...
Larry Moore Posted September 7, 2015 Author Report Share Posted September 7, 2015 Looking forward to the results... I love this sh*t... well you'll really like this one.As I said last night I went out and duplicated the finish routine aaaaand no discoloration (crap)Soooo now I was at a loss. I decided to duplicate everything (I did not round over the edges on the test pieces). Well come to find out my shaper top has/had something on it that transferred to the wood and was not removed when I sanded.I think it was tap magic that was left over from tapping new holes for a DC pickup.Needless to say I'm am a little red faced this morning. Quote Link to comment Share on other sites More sharing options...
Trip Posted September 7, 2015 Report Share Posted September 7, 2015 ==>tap magicAhhh, transfer contamination... I googled for zinc sandpaper and green speckling -- came up blank, so the sandpaper source was not looking promising... I then searched CN's blotch control and green -- also came up blank.. Glad you found it -- would have driven me crazy... ==>little red faced this morningHay, it happens... It's good that you found it... That's the important point...I've got a can of TM -- can't remember it's green -- but I do know that every time I use it, it seems to get into everything -- and it penetrates quite deeply... Wonder how much you'll have to sand back to get below it?Before repairing your project, you might want to speckle some on some scrap to see how far it penetrates... If it's too far, maybe look at some sort of plan B chemistry fix. Quote Link to comment Share on other sites More sharing options...
Larry Moore Posted September 7, 2015 Author Report Share Posted September 7, 2015 HHH The TM is not green by itself but must have reacted to the cherry. I sanded the top and washed it down with mineral spirits until the rags quit showing a stain. I will have to see what happens the next time I use it, but I think I'm good. Quote Link to comment Share on other sites More sharing options...
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