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Hollow Form Finishing

L

LANKFORD

Joined
Mar 21, 2006
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Vienna, Virginia
For those turnings with hollow insides where you cannot really see inside very well like a vase, is it necessary to try and add some finish or coating to the inside. I thought of pouring in oil, pouring out the excess and let it dry.
 
hollowform finishing

I don't know what other people do, but I do exactly what you have suggested. I have a jar of "dirty" oil...not actually dirty, just pre-used for this purpose...which I tip in, swirl around, empty back into the jar, and allow to dry off. I find this works quite well, and up to date has caused no problems whatsoever.

Andy
 
On hollow forms that have a very small opening (and you can not see into as it is too dark) - I don't use any finish at all inside. If I color the outside with dye or ? - then I dye the inside also. Depends on how large the opening is and how much you can see inside. I do not think the inside of the vessel needs any finish most of the time.
Hugh
 
Inside surface finishing

LANKFORD said:
For those turnings with hollow insides where you cannot really see inside very well like a vase, is it necessary to try and add some finish or coating to the inside. I thought of pouring in oil, pouring out the excess and let it dry.
Click to expand...

This brings up a question that's been on my mind for some time: How smooth do you finish the inside of one of these small opening hollow forms? Having never done one I'm curious. I see the hollowing tools available for use and they look like they would leave a pretty rough surface. Do you just hollow the form with one of these scraper-on-a-stick gizmos and leave it at that or is there copious sanding to follow? If so, how?
 
The few hollow forms I have done have had openings around 1.5 to 2 inches. Small, but not as small as many I see. I made a sander by taking a handball and drilling through it at both ends and putting a threaded rod into it, but not letting the rod stick all the way through. I then poured some epoxy in to fill the ball. Once it was cured I glued the j side of velcro to it and use it with velcro backed sandpaper to sand the inside of bowls. To finish it I used Electrical shrink tubing on the handle. You could certainly do this with smaller balls like a ping pong ball if you wanted. After doing this I saw a commercial product in Craft Supply or Packard that looked like the same concept in case you wanted one of these but didn't want to make it.

For hollowing I have been using the Kelton hollowing tools. They have left a pretty good surface that didn't require much sanding. The smaller the opening though the less point I see in sanding the inside. You can't get a finger in there to feel it, and you can't see into it so there doesn't seem to be a point.

I am curiuos though. For those of you who do work for galleries......how do you handle the inside of hollow forms? Do you have a higher standard of finishing for the inside of those narrow opening hollow forms than the rest of us duffers might?

Dave
 
When I do hollow forms, I try to sand any visible inside to a relatively high degree. Since lots of my forms have large open areas and voids, this means sanding to a high finish. Believe me, it's a true pain sometimes and often better done with the lathe off and locked. For anything that is not easilly visible on the inside, I sand any area that can be touched when reaching into the top with a finger and leave the rest as is.

Dietrich
 
dkulze said:
When I do hollow forms, I try to sand any visible inside to a relatively high degree. Since lots of my forms have large open areas and voids, this means sanding to a high finish. Believe me, it's a true pain sometimes and often better done with the lathe off and locked. For anything that is not easilly visible on the inside, I sand any area that can be touched when reaching into the top with a finger and leave the rest as is.

Dietrich
Click to expand...

This has been my approach too. As for finishing, I think you have to consider the climate where the piece will be displayed. Sealing helps stabalize the woods expansion and contraction. On the other hand, as Hugh hinted, depending on what the outside treatment will be, the inside needs to be considered in relationship both visualy (if you can see in) and its' effect on whatever you apply to the outside surface. If you pour a finish into a vessel that is porous, oak for example, it'll bleed righ through.

- Scott
 
Since I am still not done with my taxes and my wife isn't around I thought I would take another break and delve into this topic. When I first started turning I bought the ellsworth video and took one piece of his advice to heart. If you can see it or touch it sand it. As was mentioned I too use a sanding ball. I have a few of these I made in different sizes and a few of them with bent bars and small balls to reach those hard to reach places. I like for my balls to have a bit of give to them so I use the small wonder balls out of the machines at the grocery store and mount them on 1/4" drill rods. I originally used dowels for the stick but they too often broke if I shoved it into a tight corner.

As for finishing the insides of hollow forms I have 3 approaches. 1) If I can see, touch it and properly finish it the same way as the outside I do it. 2)If I can see it but can't finish it I spray paint it flat black, I also do this some times when I can see and finish it if it lack any interest on the inside and I want all the interest to be focused on the outside. For example on wide, short, flat hollow forms with small openings and interesting grain on the top. I have also painted the the inside of uninteresting pieces a matching color to any inlace I often add. 3) Lastly if I can't see it or touch it I often times spray it clear poly or lacquer depending on what i have on hand. The one reccomendation I have is if you oil the outside don't use acrylic spray in the inside especially if you can see it. On an oil free piece that you want to add color to spray away with what ever type you like.
 
Brief caveat.....

Friend tried the "pouring some in and swirling it around" process on a finished piece. Unfortunately, used a water based finish. Poured it in, swirled it around, vase go boom.

Lesson to learn: Don't put a finish that will swell the wood on the inside of a dry vase.

Dietrich
 
How to sand a weed pot

If you wanted to sand the inside of a hollow form with a small opening go to the beach use a screen to separate some sand into course fine and ultra fine. Fill the hollow form about half full of the course and put a plug in the opening and turn your lathe on at a very low speed. This would work like a rock tumbler, let it run for a couple of days and change to a finer grit and repeat the process. So you will be prepared when someone breaks out their fiber optic light can camera to examine the inside of your vase. :D
 
If a vase has a relatively small opening (1" - 2") then you only have to sand the top inside part of the vase where probing fingers will feel the smooth surface. With these vases, people will assume the rest of it is finished the same way.
 
Myrel Willeford said:
How to sand a weed pot

If you wanted to sand the inside of a hollow form with a small opening go to the beach use a screen to separate some sand into course fine and ultra fine. Fill the hollow form about half full of the course and put a plug in the opening and turn your lathe on at a very low speed. This would work like a rock tumbler, let it run for a couple of days and change to a finer grit and repeat the process. So you will be prepared when someone breaks out their fiber optic light can camera to examine the inside of your vase. :D
Click to expand...

Interesting idea, tried and true?? I suppose you could also purchase sand of varying grits....for people not near the beach. Perhaps reuse it too?
 
David Somers said:
I am curiuos though. For those of you who do work for galleries......how do you handle the inside of hollow forms? Do you have a higher standard of finishing for the inside of those narrow opening hollow forms than the rest of us duffers might?
Click to expand...
I thought that was the reason for the small opening:p.
I don't worry about it unless it is flared opening typical of a true vase form and then only down as far as can be easily seen. The inside of my Cremation urns such as my avatar always have lids which I finish inside and out but I don't worry about the urn itself except for the threads on the inside of the opening.
 
Myrel Willeford said:
How to sand a weed pot

If you wanted to sand the inside of a hollow form with a small opening go to the beach use a screen to separate some sand into course fine and ultra fine. Fill the hollow form about half full of the course and put a plug in the opening and turn your lathe on at a very low speed. This would work like a rock tumbler, let it run for a couple of days and change to a finer grit and repeat the process. So you will be prepared when someone breaks out their fiber optic light can camera to examine the inside of your vase. :D
Click to expand...
Have you had any success with this?
Beach sand has a reputation for being dull from all the tumbling in the ocean.

I never sand inside a hollow form and some have large opening. Just use a scraper to smooth any tool marks from the cutters.
 
Last edited:
hockenbery said:
Have you had any success with this?
Beach sand has a reputation for being dull from all the tumbling in the ocean.

I never sand inside a hollow form and some have large opening. Just use a scraper to smooth any tool marks from the cutters.
Click to expand...
Those posts were from 2006. I doubt that many of them are still with us. ;)
 
I always do an epoxy swirl/rub and then wipe out the excess. Best done after the first round of finishing (barrier / sealer) - that way any smudges or drips can be wiped and then sanded along with the sealer sanding.
Aero-Marine 300 is a low viscosity and gives lots of working time.
As I understand, the least effective water vapor barriers are wax followed by the wipe-on oils.
Then the wipe-one combos.
Lacquer is next
Best best are the urethanes and epoxies
You can never completely stop water vapor but you can slow it which allows the wood time to move without cracking.
 
I like some kind of finish on the inside as well. It helps stabilize the wood movement somewhat. I often flock the inside, which reduces some sanding and gives an interesting touch.
 
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