Question for turners

[Scott Coffelt]

I picked up some blanks to make bowls as xmas gifts. I have never worked with Ambroysa Maple, well I finished a bowl out of Zebrawood and it turned out fine. I turned a bowl out of Brazilan Cherry and it looks great. Another out of Cocobola and finally another out of Bocota. The wood has all sat in my shop for a week. Well anyway, I started turning the bowl out of the ambroysa and stopped for the night. I had just done the outside only. This morning I went to finished it up and the damn thing is cracked all over the place. Is it me, my shop or something else? Does this wood always crack like that? I have another blank, but I am really thinking on returning and exchanging for another wood.

I tried my first square bowl today and boy was it interesting. I will post pics tomorrow possibly, but in all it turned out alright. I was just finishing up the edes when it chipped on one corner. I had to round the edges a little to get rid of the crack. The finish turned out great. I made it out of Cocobola. I have another blank, so I may try another square bowl and hopefully it will turn out totally square.

[Tom Sweeney]

While I haven't used ambrosia maple yet - it's not unusual for a bowl blank to crack if left on the lathe like that. I do the same thing fairly often (leave the half turned blank on the lathe) I've had fairly good success with a couple of tips.
1.) Soak the blank really well with a finishing oil
2.) either tightly wrap a plastic bag around the the whole blank & faceplate (or chuck) & tie it closed or use rubber bands at the headstock.
3.) sometimes instead of the plastic bag - I'll stick the whole thing in a paper bag full of shavings - again after coating it with oil.

Hope this helps

[Don Farr]

Well Scott, I am just a beginner with the turning but the little oak bowl that I recently turned is also cracking and I have 10 coats of BLO on it. In fact I was going to post a question about it this morning. We will just wait and see what the experts have to say.
Tom, What kind of finishing oil do you recommend? Also have you ever had one crack after the finish, like me?

[Richard Gillespie]

Our local Woodcraft had a 10% off sale yesterday and as a enticement to bring more people in they had turning and hand carving demonstrations. One of the turners told me that he turns bowls out of green wood and that they are taken down to 1" thickness. He then told me that the bowl is treated with 50/50 solution water and dish washing soap (I believe that what he said). The bowl is then wrapped in a paper bag and allowed to sit for 5 or more weeks. The dish washing soap replaces the water in the wood.

Another turner said the longer it sits the better. But even with that treatment some bowls give problems. I saw one they were working on that after a week of sitting was checked all over the place. The turner decided to take it to final dimensions and see what happened.

[Gary Hern]

Hi Scott,

You didn't say whether the bowl blank was freshly cut or if you purchased it from somewhere like woodcraft or craft supply. Many bowl blanks you purchase are not kiln dried like furniture grade wood. Some of it may be air dried between 15 & 20%, but for the most part, it is cut green, ends sealed, and put out for sale. Depending on how long it sets in stock will dictate the dryness.

First off, ambrosia maple is not much different than any other maple or any wood for that matter, in it's drying charactics. Whey you turn green wood, you have ot resign yourself to knowing that it is going to move. The part of the tree will dictate as to how much it will move. Limb wood or wood from trees growing on the side of hills will be reaction wood. It grows under stresses that want to release when you make it thinner. Having said that, these cracks start smaller. When cellular shinkage occurs, the drying stresses creates small hair line cracks. As the wood dries more, these cracks can literally split a bowl in half in time. More often than not, they are just annoying cracks. You don't have to let all woods set over night before they start cracking. Some of the exotics (snakewood, ebony etc.) will crack while your turning it if it is not dried. Heat buildup during turning with dull tools or from sanding causes water to leave the wood much quicker. I suggest if you are going to turn from green wood, you learn as much as you can about it. There are a few books that will teach you on this. There is much information on the internet on how to handle wet wood. You have to slow the drying process, giving the wood time to conform to the differing stresses. If it dries too fast, it cracks! Simple as this. There are things you can do. If you are turning a bowl and will get back to it in the morning, wrap it in a plastic bag or some plastic wrap like Saran Wrap to seal it. You can drop it in dish detergent or plain water for that matter to stop drying. The soap soak method has many advocates. Personally, I don't like it other than throwing it in a soap solution till I can get back to it.

When rough turning wood, you have to take it to a uniform wall thickness from top to bottom. If you don't, the stresses in the thicker areas from the drying will cause cracks. The recommended thickness for rough turning is 10% of the total diameter. Meaning a 10" bowl would get turned to 1" thickness. I would like to add that the base or foot of the bowl should be slightly (maybe 10%) thinner, because that is where the stresses are greater because of the shape. At that point, you can microwave, soap soak, double bag, coat the ends in green wood end sealer, boil, or whatever technique you decide to use. Microwaving and soap soaking seem to b e the most popular for the new turners becasue they allow a person to take the bowl to finish dimensions sooner. Drying in a double paper bag will take months, while a microwave will do it in hours or days. You can also finish turn the bowl to final thickness in one setting but you have to resign yourself to knowing that the wood will warp and be more of an "art bowl", but you have to have thin walls, or you are still prone to cracking. Del Stubbs video (highly recommended and one of my personal favorites) will show this. I could go on forever on this topic, but I tried to hit the high points and different directions you can go with this. I hope it helps. If not, please ask more specific questions and we'll try to help.

Gary

I picked up some blanks to make bowls as xmas gifts. I have never worked with Ambroysa Maple, well I finished a bowl out of Zebrawood and it turned out fine. I turned a bowl out of Brazilan Cherry and it looks great. Another out of Cocobola and finally another out of Bocota. The wood has all sat in my shop for a week. Well anyway, I started turning the bowl out of the ambroysa and stopped for the night. I had just done the outside only. This morning I went to finished it up and the damn thing is cracked all over the place. Is it me, my shop or something else? Does this wood always crack like that? I have another blank, but I am really thinking on returning and exchanging for another wood.

I tried my first square bowl today and boy was it interesting. I will post pics tomorrow possibly, but in all it turned out alright. I was just finishing up the edes when it chipped on one corner. I had to round the edges a little to get rid of the crack. The finish turned out great. I made it out of Cocobola. I have another blank, so I may try another square bowl and hopefully it will turn out totally square.

[Gary Hern]

Well Scott, I am just a beginner with the turning but the little oak bowl that I recently turned is also cracking and I have 10 coats of BLO on it. In fact I was going to post a question about it this morning. We will just wait and see what the experts have to say.
Tom, What kind of finishing oil do you recommend? Also have you ever had one crack after the finish, like me?

Hi Don, sealing of any type of finish will not be a replacement for the proper treatment of wet wood. Oak from what I understand is a difficult wood to dry. I haven't turned any other than for tool handles and just practice wood when I first started turning. BLO will not slow the drying process enough to work as a sealer. It is too thin and allows moisture to leave too quickly. IF you finish turned wet wood, you still have to let it dry before it will accept oil finishes very well. It will still take some of the finish, but it will stay on the surface or at the least be a very shallow application of the oil. Oil builds according to the density of the wood. The first few coats soak into the dried fibers and creates depth. The subsequent coats bind into the previous coats and you basically build a thicker finish. The moisture of the wood will keep the oil from soaking in very far. Also, if you had turned your bowl thinner, alleviating stresses from drying, chances are, it may not have checked or cracked. It may still have done so, it's a chance you take turning green wood. I always let my natural edge bowls that I turn green dry before final sanding and finish application. You'll get a much better finish. Some moisture from green wood can give your finish a haze or cloud effect also.

[Gary Hern]

I've never known anyone that has good success with finishing oil in this application. Green wood end sealer is much less expensive and works much better. I don't think you can get enough finishing oil on a piece to stop much evaporation. Another thing that will work is a paste wax. Make sure you do not use one that will inhibit your final finish from adhering. Beeswax thinned with mineral oil or turps will work also, but again, it's more expensive than the end sealer. Have any others had good success with this, and with the prohibitive costs assosiated and you seeing enough positive to outweigh the negatives?

While I haven't used ambrosia maple yet - it's not unusual for a bowl blank to crack if left on the lathe like that. I do the same thing fairly often (leave the half turned blank on the lathe) I've had fairly good success with a couple of tips.
1.) Soak the blank really well with a finishing oil
2.) either tightly wrap a plastic bag around the the whole blank & faceplate (or chuck) & tie it closed or use rubber bands at the headstock.
3.) sometimes instead of the plastic bag - I'll stick the whole thing in a paper bag full of shavings - again after coating it with oil.

Hope this helps

[Scott Coffelt]

It was completely coated with wax.

[Bill Grumbine]

Is it me, my shop or something else? Does this wood always crack like that?

Hi Scott

Gary has given you some very good information on possible problems. I would add that the number of variables is so high that it is almost impossible to pinpoint a cause without seeing the wood in person. In your case, more experience with turning blanks in general and maple in particular will help you out some.

It is hard to say whether or not it is that particular piece of wood, but it may have been. My experince with various maples is that they are for the most part stable, with the exception being sugar maple, a.k.a. hard maple, rock maple, etc. That stuff likes to crack for me. However, ambrosia maple is a red maple (usually) which is somewhat softer (soft being a relative term) and is less prone to crack.

It may be that the wood was stressed before it was processed. It may be that it was improperly processed, and that can mean a number of things, from drying too fast before it was waxed, to being cut from the log in a way that would contribute to cracking due to unbalanced stresses in the wood. it might have been on top of a pile in the sun somewhere, or stored where it was hot and dry.

As Tom mentioned, it is generally not a good idea to leave a partially finished blank on the lathe. It can be done with proper precautions, but not just left out in the air. I wrap mine with a plastic bag even if I am just stopping for lunch. This works well enough that you can leave it for a while. In fact, the day after Thanksgiving, I was turning a piece of wild cherry for a customer's order. I was experiencing some back pain, which turned out to be tendonitis in my tailbone area, and I was laid up until this past Monday. I was unable to finish that bowl, getting just the outside shaped.

I wrapped it in a bag intending to finish it off the next day, not knowing that I would be incapacitated for over a week. When I got back into the shop and unwrapped it, I discovered that the bag had water in it, and some rust had formed on my chuck, but the wood had not moved or cracked at all! That is saying a lot for wild cherry, which is notorious for splitting all over the place.

Still, it is not a good idea to let it go that long. Whenever you cut into a piece of wood, you are changing the stresses on that wood. If you can do a complete roughing out in one session, you will be much more successful in keeping the wood from cracking.

Good luck with it.

Bill

[Tom Sweeney]

I did not intend for my post to be the "proper " way to deal with green turning blanks. Gary touched on the right way to do it.

In my case - I don't get a lot of shop time so I have to sneak a little bit in when I can. If I start a bowl & have to leave it before I rough turn it inside & out to a thickness of 10% of the width then I often use the method I described. Usually I'll use tung oil or a salad bowl oil that doesn't color the wood (yes this is certainly more expensive than wax). Certainly a wax emulsion or end grain sealer would be prefered - but if it's 11 pm & I'm getting to tired to continue I simply soak the bowl with the oil - rub it in a little with the lathe turning & then put a little more on & wrap it in a plastic bag. This is if I figure I'll get back to it the next day - though I've had them sit for days without cracking. I figured that this was the type of situation that happened to Scott. It seems to work pretty well for me, then again it's possible that the humidity level in my uninsulated block 2 car garage is a high enough level that it helps to keep the bowl from dying out to fast.

PS: Sorry to here about your back Bill.