[Cob] Finish Coat Help Needed

[Stephen Karrington]

> On Wed, 12 Mar 2008, Stephen Karrington wrote:

> [snip]
>>> Without knowing exactly what went in to this finish, any recommendation
>>> that would work would be a lucky guess.  What exactly is the mixture of
>>> this finish coat?
>>
>> I'm guessing its clay powder and color. I don't think anything else is
>> in it. The only other thing that might be in there would be tapioca
>> flour. And oil/wax combo was put on top.

> You misunderstood me, I was wanting to know what was in the mix that made
> the surface oily.

It was a combination of vegetable oil and beeswax.

> You don't mention the type of oil or wax that was 
> applied, however, you only really have two options, find a way to harden
> the oils on the surface or remove the finish coat down to a level where
> the oil/wax didn't reach, because anything you attempt to put over the
> surface is unlikely to bind to an oily surface.  If it was me, here are
> things I might try:

>    - Talk to a chemist friend of mine about anything I might apply to
>      harden the wax/oil (this would require knowing what oil(s) and wax(es)
>      were used.

>    - Apply high heat to the surface in hopes of possibly polymerizing the
>      oils/waxes, this of course runs the risk of igniting the surface and
>      possibly the rest of the building around it.

>    - Use a torch and attempt to burn the oil/wax off the surface.  Of
>      course this runs an even greater risk of igniting anything in the
>      surrounding area.  Fumes might be rather nasty or toxic depending on
>      just what was applied.

> NOTE: I don't recommend using raw linseed oil for these types of
> applications as it just doesn't dry completely.  There are some non-toxic
> varieties of boiled linseed oil.

I am not sure what kind of linseed oil we have here. It looks like its
from Holland. I can send a photo of a container. Maybe someone knows
this brand. I don't know if its raw or what. But I'm pretty sure its
on the natural side as the smell is pretty good. Here in Thailand no
one seems to know much about anything. So asking the distributor we bought
it from doesn't accomplish too much.

Should I boil the linseed oil next time I apply it? We didn't boil it last time. Just
put some in a container and brushed it on.

Thanks.

S