• It's time to cast your vote in the January 2025 Turning Challenge. (click here for details)
  • Conversations are now Direct Messages (click here for details)
  • Congratulations to Alan Weinberg for "Elm Burl Bowl" being selected as Turning of the Week for January 27, 2025 (click here for details)
  • Welcome new registering member. Your username must be your real First and Last name (for example: John Doe). "Screen names" and "handles" are not allowed and your registration will be deleted if you don't use your real name. Also, do not use all caps nor all lower case.

What is this mark on my hollow form?

Grey Darrah

Grey Darrah

Joined
May 6, 2018
Messages
74
Likes
28
Location
Cartersville, GA
This is a 9 inch wide by 6 inch tall cherry side grain hollow form that I just finished with some oil. It was sanded glass smooth up through the grits to 2000. You can see in the image a horizontal line in the side of the form. Any idea what this is? It looks like a tool mark (almost like a faint catch), but running my finger over it is perfectly smooth with no indentation whatsoever.

Thanks,
Grey

_Y7F4502.jpg
 
Nice lookin form.
Blemish forensics....
It could be bruised grain. From a tool or a lathe steady.

I’m thinking it is slightly torn grain from cutting a little bit in the wrong direction past the high point of the form.
It looks like more finish is absorbed giving a muddy look.

It is also the back side of the endgrain which is always the worst cut even when cutting toward the large diameter a little bit of the cut is going up and you can get some torn grain here.
This is always the spot to inspect. More shrear scraping before sanding.

63CC50B8-9F43-424B-82D9-6B1BB35FED40.jpeg
 
Last edited:
just an opinion....that is sapwood where nutrient are carried...maybe muddy water carried up the tree.....there is a white mark going all the way into the heartwood.....looks like stem that never became a limb......jmo
 
another thought.....if form turned with green wood....sanded while green heartwood sanding dust pushed into sapwood by sanding
 
I'm in the bruised or compressed fiber camp. I can usually see torn grain during the initial sanding, bruising usually doesn't show until it soaks up the finish a little more then the surrounding wood. Is the area shown by the blue arrow inline with the blemish shown by the black arrow? Any more clues on the other side?
Bruised vase.jpg
I really like the bark and that little wavy edge at the opening. It's no fun to start the sanding schedule again but for this piece I would.
Nice work...
 
My guess is bruised wood from the gouge. I grind the heel or bottom corner off of the gouge so that is not a sharp edge. When your turning and have this sharp edge of you pause or slow down it's very easy to bruise the wood or compress the fibers and no amount of sanding will get it out. It normally looks like a light colored ring but I've seen dark. The tell tale sign is the fact that it follows rotation of the wood which tells me it almost has to be the gouge problem.
 
Clifton C said:
I'm in the bruised or compressed fiber camp. I can usually see torn grain during the initial sanding, bruising usually doesn't show until it soaks up the finish a little more then the surrounding wood. Is the area shown by the blue arrow inline with the blemish shown by the black arrow? Any more clues on the other side?
View attachment 25938
I really like the bark and that little wavy edge at the opening. It's no fun to start the sanding schedule again but for this piece I would.
Nice work...
Click to expand...

I agree with Clifton. I also see what looks like some parallel marks. All were probably caused by the way that the bowl gouge was presented to the wood.
 
I think I'm in the "bruised" camp as well. It's too late to go back to sanding though. It's already been sold and delivered. The client was thoroughly pleased. I was just wondering for future projects.

Thanks,
Grey

Clifton C said:
I'm in the bruised or compressed fiber camp. I can usually see torn grain during the initial sanding, bruising usually doesn't show until it soaks up the finish a little more then the surrounding wood. Is the area shown by the blue arrow inline with the blemish shown by the black arrow? Any more clues on the other side?
View attachment 25938
I really like the bark and that little wavy edge at the opening. It's no fun to start the sanding schedule again but for this piece I would.
Nice work...
Click to expand...
 
This is not bruising but torn grain. Cause could be a tool that needed sharpening ..or... you forced the cut just I bit to hard causing it to “pull” on the fibers as you made the cut.
Shear scraping or re sharpening your tool and then making a final “light” cut would have removed this blemish.
This one line is most prominent but I also see more of this “torn grain” below where you have highlighted.
A few very light shear cuts with a freshly sharpened gouge is the solution.
 
So if you're green turning to final dimensions, how do you deal with this? When I finished the hollowing, I sanded the outside up to 2000 and it all looked great. Then I set it aside to dry for a week. The marks only showed up when I put the first finish coat on. At that point, the vessel is out of round and can't be shear scraped.

For the future, what would you recommend?

Thanks,
Grey

John Spitters said:
This is not bruising but torn grain. Cause could be a tool that needed sharpening ..or... you forced the cut just I bit to hard causing it to “pull” on the fibers as you made the cut.
Shear scraping or re sharpening your tool and then making a final “light” cut would have removed this blemish.
Click to expand...
 
Grey Darrah said:
So if you're green turning to final dimensions, how do you deal with this? When I finished the hollowing, I sanded the outside up to 2000 and it all looked great. Then I set it aside to dry for a week. The marks only showed up when I put the first finish coat on. At that point, the vessel is out of round and can't be shear scraped.

For the future, what would you recommend?

Thanks,
Grey
Click to expand...

Maybe shear scrape as a precautionary measure whether the piece needs it or not.
 
I do not know what caused it but I have had the dark blotches on sap wood in cherry but not lines. A solution is to sand the affected area when it shows up. A friend of mine does that and says "you are the only one who will ever know" .
 
I now try do do a few final very light shear cuts on all my pieces, whether I think they need them or not.
If you pay close attention when you start sanding this light blemish of torn grain will often start to show up only after you’ve reached 240 or higher in your grit sequence. So pay close attention, often it can still be removed through sanding by going back to your starting grits but that may not always be the case, you may still end up going back to a shear cut to remove it.
 
Welcome to the world of tear out.... That form is turned in side grain, or bowl grain orientation. Every time you cut uphill against the grain, you will get a tiny bit of tear out. Learning to manage it to get it down to minimal amounts is the trick. I do prefer a shear scrape for finish cuts. Generally, the higher the shear angle, the cleaner the cut (I do have a shear scraping video up on You Tube). Learning to see it is an 'experience' thing. Some times you have 95% of it sanded out and it is really difficult to see. I almost never sand beyond 400 grit, but have had pieces where the tear out was invisible till I put on the finish. Some times tear out like you have will be invisible at 400 grit, but going up to 2000 will make it highlighted... I do hand rub each piece as I sand, and that can push the dust down into the minor tear out, and highlight it. Some will use a bit of finish to help high light it as well. Having good light is crucial as is having good glasses. You can also take it out into direct sun light as we see better in that than we do with most shop lighting... "Never take a finished piece from the shop into the house on a sunny day. Sunlight causes scratches!" The light will reflect/refract off of tear out differently than the untorn wood. I have been going through a bunch of myrtle that is extremely prone to tear out. 600 grit CBN wheel edge is best bet for cutting it out. Also, before you start to sand, run your hands over the wood in both directions of rotation to 'feel' where the tear out is, then as you sand, spend some extra time in the tear out areas. It can be sanded down to unfeelable range, but you can still see it...

Oh, what is the wood? Mesquite???

robo hippy
 
I appreciate the suggestions and am going to try to improve my shear scraping.

The wood is black cherry.

Thanks,
Grey

robo hippy said:
Welcome to the world of tear out.... That form is turned in side grain, or bowl grain orientation. Every time you cut uphill against the grain, you will get a tiny bit of tear out. Learning to manage it to get it down to minimal amounts is the trick. I do prefer a shear scrape for finish cuts. Generally, the higher the shear angle, the cleaner the cut (I do have a shear scraping video up on You Tube). Learning to see it is an 'experience' thing. Some times you have 95% of it sanded out and it is really difficult to see. I almost never sand beyond 400 grit, but have had pieces where the tear out was invisible till I put on the finish. Some times tear out like you have will be invisible at 400 grit, but going up to 2000 will make it highlighted... I do hand rub each piece as I sand, and that can push the dust down into the minor tear out, and highlight it. Some will use a bit of finish to help high light it as well. Having good light is crucial as is having good glasses. You can also take it out into direct sun light as we see better in that than we do with most shop lighting... "Never take a finished piece from the shop into the house on a sunny day. Sunlight causes scratches!" The light will reflect/refract off of tear out differently than the untorn wood. I have been going through a bunch of myrtle that is extremely prone to tear out. 600 grit CBN wheel edge is best bet for cutting it out. Also, before you start to sand, run your hands over the wood in both directions of rotation to 'feel' where the tear out is, then as you sand, spend some extra time in the tear out areas. It can be sanded down to unfeelable range, but you can still see it...

Oh, what is the wood? Mesquite???

robo hippy
Click to expand...
 
Dude - you do good work.
The pics in the other post are from my first effort at black cherry - here in N. Texas, we don't get much, if any.
I found it incredibly hard and a hard material on tools - the mark seems to be from a gouge - those last cuts need to be slow and with a, not merely sharp, but a pristine edge.
I then cheat: I put a 5" hard pad on my 3" buffer (never on a DA sander), put the lathe at about 200-rpm, and lightly kiss the surface with a 7-o'clock cut. Takes out the tool marks and, with 80-grit, even a few minor bumps. If a valley is left due to a slight concave spot, it shows and I know exactly where I need to do the old TSC (tight sphincter cut).
John
 
Thanks for the compliment. You got me cracking up over the TSC comment.

Now if I could just step up my finishing game to even half what yours is... I read a thread describing your method and it's more involved than I can handle for now. I'm going to try some spray can lacquer and polishing compound and see where that gets me. I'm really wanting that dipped in glass look you've perfected.

Grey

John Tisdale said:
Dude - you do good work.
The pics in the other post are from my first effort at black cherry - here in N. Texas, we don't get much, if any.
I found it incredibly hard and a hard material on tools - the mark seems to be from a gouge - those last cuts need to be slow and with a, not merely sharp, but a pristine edge.
I then cheat: I put a 5" hard pad on my 3" buffer (never on a DA sander), put the lathe at about 200-rpm, and lightly kiss the surface with a 7-o'clock cut. Takes out the tool marks and, with 80-grit, even a few minor bumps. If a valley is left due to a slight concave spot, it shows and I know exactly where I need to do the old TSC (tight sphincter cut).
John
Click to expand...
 
Last edited:
That's a gouge mark/rough patch that was not sanded out with the first grit. If you look carefully, it would be pretty visible. Good low angle lighting is important, and I lightly wet the piece between grits-it will make those sort of thing more visible. Fixing that kind of thing with your first grit is so important, whatever that grit might be. Don't be afraid to start with a grit coarser than you think it needs-it makes quick work of repairing any damage/tool marks.

I see those marks a lot-it's a common problem.

John
 
You must log in or register to reply here.
Back
Top