I should have been more specific. These bowls are dry, just the finish (danish oil) needs cured.
I've been looking around for some mdf. so far i've got a 8 x 12 piece so wouldn't be a very big disc. Need to get to town and buy a piece but I forget about it when there. I've tried the "making a list" thing too. and it's typical. I forget the list.
Most curing oils need *heat* to cure, Sun (UV rays) can cause undesirable discoloration I would imagine.. You can stick them in a box with a heat source (I'd research on ideal curing temperatures for the oil you are using) to heat them more evenly and maintain a constant temperature - Putting them in sun and then bringing them back in you may tend to gain moisture (from condensation) as they cool back down. Just IMHO, nothing scientific about my thoughts on it. I've put some pieces finished with pure linseed oil (polymerized) in a box with a 60 watt light bulb providing heat source for a couple days, and they seem to cure much faster than those that I had sitting out in the sunshine (One was on display at farmer's market, and sun caused oil to seep out of the pores, while the ones that had fully cured (including a small dish that I'd had in the heat box) did not have any problems.. Might be something to bear in mind (and/or research?) Did a quick look at Watco Danish oil , and they do say your results are affected by temperature and relative humidity , with ideal conditions (80 degrees, 50% Relative Humidity) being 72 hours to the "recoat" time, and I would tend to assume perhaps a bit longer for a full cure that won't weep in the sunshine... https://www.rustoleum.com/~/media/D.../English/CBG/Watco/WAT-02_Danish_Oil_TDS.ashx
Wonder what the most UV resistant finish is?
Paint
There's an idea! I could have put bondo in the hole I excavated in a boxelder bowl a little bit ago and then air brushed it and then clear coated and and... No wait I went the half a...s method and put some epoxy this time. Damn coffee grounds I couldn't get to stick in this bowls twin nor saw dust with ca. So eventually my reddish patch here is going to stick out like a sore thumb or a zit on the end of a nose when the flame goes out in this boxelder.Paint
It's just my process. I final turn a dry roughed out bowl on the outside using a friction chuck and tailstock. Then while it's still on the lathe I sand the outside. Flip the bowl around, mount in the four jaw chuck and turn the inside. Again while still on the lathe I sand the inside. Then I usually apply finish whether danish oil, shellac friction polish or sometimes tried and true or walnut oil. I remove from the lathe and set aside for the finish to cure. Then so far it's been once a week I will use the vacuum chuck and remove the tenon from the batch of bowls from the previous steps. I sand the little spot left from that and put a finish on that last spot off the vacuum chuck and the bowl is done. I have been gravitating more to just danish oil because it's pretty simple to put on the spot where the tenon was.
I turn my tenons off between a friction chuck and the tailstock live center - I learned to turn them down to a tiny cone-shaped nub that with practice you can turn down to less than 1/16 inch and then with lathe off, push in your detail gouge and rotate bowl by hand cutting through that bit of nub that is left. Granted, it does not allow for access for adding details to the bottom/foot like some folks do, but that is my process.. I don't have a vacuum chuck and so far have not really even considered one.. If not wanting to try and turn it down that fine (or don't have detail gouge that can do the trick) can turn it down to as small a nub as you can get and then slice it off with a chisel or flush cut trim saw, then sand away.
If it's working for you, that's good.
Other than paint as Charles suggested I would guess a water based poly, but this is a film finish. I tried it on an apple bowl, very little change to the color. I thinned it down and rubbed it on with a rag, worked good but it raised the grain so you have to sand between coats, I used 400 grit and applied 3 coats. When I was finishing oak trim in my house the vendor had me use the water based poly and it held the natural color with very little change over the years.
Danish oil is not affected by the sun(heat) but by oxygen. The chemistry involves polymerization of the molecules using an oxidative process. Different brands of oil vary in composition so the reaction kinetics are also different. Using the same brand for a benchmark and figuring out suitable conditions for the chemistry is your best bet for optimal conditions. Accelerating the reaction can be tough though to give you good results. In some cases trying to speed up the process can do more harm than good.
But.. But... the other day in that class I took the teacher said mostly only other turners will notice those kinds of things....... (I kind of questioned his credentials in my mind after that).It is well known that exposure to sunlight causes sanding scratches, swirls, and other defects to appear in finished bowls. Be wary
Probably mostly sometimes true... but... consider that you are also one of those "other turners" and will notice "these kinds of things". You are your first customer. If you're not happy with your work, whatever others think doesn't matter so much IMO.
Before I set up my first vacuum system (1994) I used several sized discs (with a tenon glued on the back) mounted in a chuck. To this I added 2" rigid styrofoam insulation (used to be blue or pink) with double-sided tape. Cut a groove to match your bowl rim - mount the bowl with tailstock pressure. A little compression in the foam will occur (a good thing) and then use masking tape (2") from the foot of the bowl and stretch over the disc. Depending on the size of your bowl 4 or 8 strips is usually sufficient. The tape sticks better to a finished surface than unfinished wood but will still work. Also, best to have the disc size close to your rim size (not a 6" rim and a 12" disc) because the tape will flap around in the breeze when you turn the lathe on.
Do your business on the foot - cut tape - done! The styrofoam will last a long time for many bowls and sizes and is simple to replace when needed. BTW, the styrofoam comes in handy for many things around the shop from noise & vibration reduction, shims, motor mounting, tool holders/protectors, etc.
Me too. Another advantage - I turn the lathe on a slow speed and buff with 4" wheels. The finish doesn't have to be totally cured and you will never have any burn through of the finish because the wheel is never in the same place long enough for that to happen.
Makes me wonder if you could stick it in , say, a plexiglas box, and then add in some bottled Oxygen (from a mapp torch kit or oxyacetylene welding set) if that O2-rich environment might accelerate the process...
Doug, if I understand you buff while the piece is held by the tendon in the lathe. If so, can you explain this better and what speed you are turning the bowl. Also are you holding the buffing wheel by hand?
Tenon held in the chuck mounted on the lathe. I use 6” buffs in a 1/2” hand drill that goes to 2400 rpm I think, which matches surface speed of an 8” buff at 1800. I buff at this speed, then dial the speed back to ~1800 drill rpm for carnauba wax.
I'm probably going to switch to this way because I'm mostly using danish oil these days and I don't think it's necessary to use the lathe. Before I was using it to friction polish some bowls and other finishes as much as possible while I was waiting for my vacuum set up to get here. Needed the tenon to re-center the bowl on the vacuum chuck. Or at least seemed easiest to me that way.
How do you get rid of the recess after?
I don’t. No reason. It becomes part of the piece.
Quite a few advantages, Rusty. By using the "lathe-chuck-tenon" as a THIRD hand it is:
That’s a cool idea I had never thought of.
