Finish for hot tea cup

[John Hill]

I am visiting woodturners in France and one asked me for a recommended finish for a functional, maple, 3/16" thick tea cup to be used for hot drinks. Can someone please help?
John Hill

 

[n7bsn]

For hot drinks, and drinks with alcohol I use Envirotex

 

[SMarlow]

I would use Waterlox.
Good adhesion, easy to work with, stain resistant, food safe (when cured) and heat resistant (according to their website "Generally objects as hot as boiling water (212 degrees) will not harm your Waterlox finish." ).

 

[Barbara Gill]

John, this is a very interesting question which surfaces every once in awhile. I never have given it much thought except to think about the early settlers who sometimes used wood for their eating surfaces.

I use a penetrating oil which is not Waterlox. It is a little thinner than Waterlox and penetrates wood well. I am going to do an experiment where I will use a fairly soft hardwood which allows the easy penetration of the oil. I am going to allow the oil to soak completely through the wood, cure and experiment with boiling water.

I do know that if you put a pan of boiling water on a surface that has been finished with this oil, it will raise the grain slightly.

 

[C Edward Moore]

Alcohol safe?

I checked out the link to Envirotex. It mentioned applying a second coat of this finish and prepping the surface by wiping with a clean cloth and then with alcohol. There are two possibilities here. The alcohol wipe might simply be a means of cleansing the surface. OR, it might be a chemical reaction designed to have the second coat adhere better to the first coat. If this is the case, then an alcohol drink in a coated goblet could be reacting with the Envirotex.

 

[n7bsn]

I checked out the link to Envirotex. It mentioned applying a second coat of this finish and prepping the surface by wiping with a clean cloth and then with alcohol. There are two possibilities here. The alcohol wipe might simply be a means of cleansing the surface. OR, it might be a chemical reaction designed to have the second coat adhere better to the first coat. If this is the case, then an alcohol drink in a coated goblet could be reacting with the Envirotex.

That's process is to ensure the finish is clean

 

[Jake Debski]

John, this is a very interesting question which surfaces every once in awhile. I never have given it much thought except to think about the early settlers who sometimes used wood for their eating surfaces.

I use a penetrating oil which is not Waterlox. It is a little thinner than Waterlox and penetrates wood well. I am going to do an experiment where I will use a fairly soft hardwood which allows the easy penetration of the oil. I am going to allow the oil to soak completely through the wood, cure and experiment with boiling water.

I do know that if you put a pan of boiling water on a surface that has been finished with this oil, it will raise the grain slightly.

Barbara,

Do you think submerging the object, in the oil, for a couple of days would be of value?

 

[Barbara Gill]

Jake, I don't know. Maybe one of the Norfolk Pine turners would have some input. Anything I would do would be an experiment. I do know that porous woods like cottonwood can be soaked through just by filling up the object with oil as long as the wall thickness is not real thick.

 

[dkulze]

The main thing I've come to know about wood pieces meant to be used with food, is to expect discoloration and change in finish over time. Only fully plasticizing it with epoxy and including at least a thin surface layer will prevent this, in my experience.
If treated well with a polymerizing oil or, even better, an acrilic finish (CA, epoxy), you'll get an outer surface that will remain attractive and an inner surface which will discolor somewhat but will remain even with care. It's just a relative hassle.
Was it the Japanese or Chinese that did this for teawear by using many coats of laquer? Or did they only do this to metal or pottery?

Dietrich

 

[Ed_McDonnell]

Barbara,

Do you think submerging the object, in the oil, for a couple of days would be of value?

If you are not going to turn thin and try and get a translucent effect I don't think you will gain anything by soaking in oil for an extended period. Additionally, in my experience, Norfolk Island Pine that has been soaked in BLO will "sweat" oil when it gets warm/hot until it is sealed. I would not use a cup that has been saturated with oil for hot beverages, even if it had been sealed. But that's me.

Another finish to consider is a very thin penetrating epoxy (similar to what is used to fortify rotted wood).

You could make up a series of maple squares the same thickness the cup will be turned and finish them with different finishes. Boil each of them for a couple minutes and see what happens. Protecting the wood is just one consideration. What might leach out of any finish you use should probably be just as much of a concern. A degraded finish or discolored / smelly / foaming water would be a bad sign.




Ed

 

[GeorgeH]

"...If this is the case, then an alcohol drink in a coated goblet could be reacting with the Envirotex.

Not necessarily, Ed. Industrial alcohol (e.g. isopropyl, methyl alcohol, etc.) are not the same as ethanol or ethyl alcohol. But, in any case, I think it might be a good idea to test the finish to be certain. Kinda like what Barbara has in mind but with a different liquid.

 

[Bob Boettcher]

The Envirotex Lite is an amine-cured epoxy coating. If it is properly mixed and cured it should be safe to use for food. All pop cans are coated inside with epoxy, for example.

The alcohol wipe between coats is only for cleaning, it will not attack the epoxy coating.

Bob