Supersized hollowform completed

Elaine's hollowform. Bowl gouge included for perspective.

In an earlier post I discussed the construction of the tools I needed for turning large hollowforms. I had roughed out the form prior to drying which was to be the next step in the process. I feared the piece might crack. Much to my dismay, the drying process initialized a crack  at the opening as well as some small cracks on the bottom. The top crack would affect the appearance while the bottom cracks were minute and were to be turned away in the finishing process.

Cap detail

To say the least, I was upset. I was able to halt the cracking with CA glue, then watching it a couple of times a day while the piece continued to dry. Finally it had lost enough water that the weight stabalized and was ready to finish turn; about three months, as I had anticipated.

RED! applied.

During that time I thought of various ways in which to turn this disaster into a “design opportunity”. Originally, I had planned on making a cap to close in the opening much like “Black on Black” and “Blue Planet” (see gallery). Continuing on that idea, I envisioned wings or leaves eminating from the cap and finally settled on the design in the photograph, encorporating a bit of texturing to add some interest and contrast with the gloss finish. The shape of the cap also corrected the line of the form that had turned too sharply at the top when turning much of the crack away. In the end I actually felt that the final product was more dramatic than the original concept. To say the least, I was very happy with “the save”.

RED! sanded back.

The original blank weighed 40 lbs. After initial turning it weighed 10 lbs. After drying (loosing about 5 lbs. of water) and finish turning, the piece weighed 4 lbs. – 10 percent of its original weight.

The customer specified a reddy orange/yellow colour combination that I had applied to a Zen Candle that she had purchased earlier. After bleaching the piece twice I applied a red dye which was then sanded back, exposing new wood. Yellow was applied to achieve the final result. If you notice there is an airbrush in the photos. I have had issues with colour contamination in my applicators and dye containers. Using an airbrush eliminates contact with applicators that pick up the original colour from the work. The cap was painted black and textured after turning and carving to shape. Both were finished with (I forget how) many coats of Wipe On Poly.

Yellow applied.

On a sad note, the remainder of the wood that I bought for the piece cracked severely. There is enough to make two more pieces the same size so that is quite a loss, however I have another “save” in mind that may make them equally as spectacular. Here’s hoping!

As always, I encourage your comments and questions, so please refer to the tag line at the bottom of the article to post a comment.

About Ed Pretty

I am a professional woodturner, specializing in gallery work, commercial work, teaching and demonstrating. I have been turning since 1958, so... a long time. I use this site to present my work to the public at large and to let people know that I am available for teaching private lessons in woodturning. Wood turning is one of my passions (the other is motorcycle touring). It is my desire to pass on everything that I have learned over the years to others so that the craft of woodturning will grow.
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5 Responses to Supersized hollowform completed

  1. Andy says:

    Hi Ed, What wood was this made from and how did you bleach it?

    • admin says:

      Hi Andy,
      The wood is figured Big leaf maple. It was bleached with a two part wood bleach called “lighten Up” It is equal parts hydrogen peroxide (strong oxidizer) and sodium hydroxide (strong base which releases the oxygen). Sometimes I bleach pieces several times.

  2. John Spitters says:

    Hi Ed
    So yesterday I was turning a Larger hollowform from figured maple (finished product should be apx. 12-13″h) and half way through hollowing 3 rather large cracks instantly happened. I was ready to through it out in frustration when I suddenly remembered this form (Elaines Hollowform) that you did and not knowing the reason for the large collar when I saw this piece in person, I instantly reasoned that it could be used to hide these cracks that had formed in my piece. So last night I set about glueing the cracks back together, at which point I thought to look up your piece on your blog and low and behold I see that you made your collar for the same reasons.
    So hopefully you won’t mind when you see my piece in the future with a similar collar detail.
    Thanks Ed for the inspiration.

  3. AJ says:

    Supersized hollowform completed…
    I would like a new idea on deep hollowing techniques… I use a 24″ 1 1/4″ boring bar with either 1/8″ or 1/4″ cutting tip… The blank is a 22″ deep 19″ diameter piece of walnut… No problem up to 16 to 17″ but the last few inches get very difficult… Any suggestions…

    • admin says:

      Hi AJ,

      I turn big leaf maple and it’s not as tough as black walnut but possibly the same as silver walnut so there may or may not be a direct comparison between woods for cutting resistance.

      One issue that you may consider is not the thickness of the cutter, but the size of the cutting area. For serious wood removal I use a cutter with about 3/16″ nose (tear drop shape cutter). This applies a lot less load to the cutter, hence less on the bar and less vibration. I use the larger end of the tear drop and even a broader cutter for surface clean up but these are typically very light cuts, so no issue with vibration. I get about 20″ before I have serious issues with vibration and can work to 22 – 23″ but the last couple of inches is a slow go with lighter cuts.

      Another thing I have done is put a bag of lead shot on the bar at the back end but not so far back as to interfere with the rollers. This made a big difference.

      Both the smaller cutter tip and the lead shot really helped.

      My bar is hot rolled mild steel round bar, so not incredibly strong or stiff (I descaled and polished the bottom surface). Cold rolled would be a bit stiffer because of the work hardening (and nicer to work with), but not much. One thing I have considered is shaft stock that is typically various alloyed steels; make up dependent on application. It’s usually quite stiff to prevent whipping so may help a lot but it’s not cheap. I would do this rather than going to a larger diameter. This one at 72″ is heavy enough, thank you very much. 🙂 The torque arrester is light square tubing.

      Hope that helps.


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