Poplar bowl turn how do you avoid the black spots and roughness after finishing

[u/Paddle124]

I am helping some friends get into turning by having "turning parties" where we turn bowls together.

I have been using poplar blanks-relatively soft, and inexpensive....We get a really nice surface with tools and sanding to 220 grit.. but when we apply walnut oil and then sand with 320 we get black stained areas and the surface feels really rough. I realize this is raised grain so much more pronounced than in walnut, or maple.

would you recommend: - application of sanding sealer first? -application of denatured alcohol (Jimmy Clewes technique- without "burning it off" prior to sanding? -re sand after finishing? -use a different finish?

My friends have had a great time and have a bowl as a souvenir (no funnels so far :) )- most have agreed to go on and take a real woodturning class....I want to optimize their experience with a bowl that looks and feels as good as possible.

appreciate any advice/experience you have.

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[u/mrtmrj]

I pop grain a few (2 or 3) times between switching grits with denatured alcohol. Blast it real good with compressed air to get rid of most of the dust. Pop grain. Say ooooh aaaaaah at the pretty wood I've revealed, then next grit.

You may also be lifting endgrain tear-out when applying your finish if during sanding you're burnish-ing it down into the bowl instead of removing it with your abrasive. Not sure about black spots, unless you're using a steel wool and it's reacting to tannins in the wood or finish.

Thoughts?

[u/mrtmrj → u/mrtmrj]

Replying to myself to add: This is a WONDERFUL way to get your peers hooked. Kudos to you OP for teaching and bringing others to the craft.

[u/Paddle124 → u/mrtmrj]

thank you so much

[u/jserick → u/mrtmrj]

This! Raise the grain with DNA.

[u/Paddle124 → u/jserick]

thank you so much

[u/quantumhobbit]

You could try “raising the grain”. Sand, apply water and let it evaporate, then sand again. That should help with the surface roughness.

[u/jserick → u/quantumhobbit]

This is the answer! Have you tried denatured alcohol? Evaporates super quickly.

[u/Paddle124 → u/jserick]

thank you so much

[u/Paddle124 → u/quantumhobbit]

thank you so much

[u/sparkydoggowastaken]

To add to the other people: the pores of the wood fill with dust, which feels smooth, but when it fills with liquid the grain raises itself and it feels rough again. Popping it with water then letting it evaporate will make it get rid of the dust and raise the grain, letting you sand it back down. Do this a couple times and the grain will be actually flat instead of your grain effectively being bent over.

[u/Paddle124 → u/sparkydoggowastaken]

thank you so much

[u/lowrrado]

I've had this before, I guessed the black spots are from metal dust from sharpening gouges, dust will sit in the flute. Sanding at 80 grit still didn't remove them but a light cut did after wiping gouge down after sharpening.

[u/Paddle124 → u/lowrrado]

thank you so much

[u/Glum_Meat2649]

The poplar around here is pretty much always wet and fuzzy after sanding or scraping. My best finishes are usually straight off the tool.

It rots real fast air drying, not worth kiln drying. Big Leaf maple is much better and more plentiful.

With newbies, I like to use green (wet) wood, more forgiving and pleasant to turn. If you’re looking for cheap dried blanks, I’ve found basswood to be as cheap or cheaper. Much easier to sand and finish.

[u/jserick → u/Glum_Meat2649]

To me it sounds like you’re confusing moisture content with wood characteristics. If the poplar is wet, it’s because of how long it’s been drying, not because it’s poplar. Maybe I’m just misreading your comment? Apologies if I’m just missing your point. 😊

[u/Glum_Meat2649 → u/jserick]

I’m in an area that is wood rich. Poplar rots very fast here. If you don’t turn it green right away, it gets punky and will crush in your fingers.

Most species of green wood often don’t sand or scrape well. Green poplar doesn’t sand or scrape well. Poplar is basically practice wood, if anyone bothers to go get it.

We have many better species of wood, that is worth putting time and energy into. No one I know would take a quality wood (holly, maple, birch, oak, walnut, various fruit trees and madrone) out of the kiln or drying rack, to put in poplar.

If you live where you need to buy wood, and you’re introducing new turners to bowl making, in my opinion, basswood is a better option than poplar. It sands and finishes cleaner.

[u/jserick]

Raising the grain is likely the answer, as others have said. One question though—is the rough texture around the whole bowl? If it’s only at the end grain areas, you likely are dealing with torn grain. In that case, tool and or sharpening technique are the causes.

[u/Paddle124 → u/jserick]

the entire bowl...thanks so much

[u/869woodguy]

Try a different wood.