Brooklyn has a lot of wood floors. The common finish is some toxic varnish. As a Brooklyn green floor installer we don’t use that and are constantly researching more natural floor applications. Our floors are always salvaged and usually need a good sanding and sealing.

Recently I was discussing this on an email list and got a great answer from a fellow green builder, John Salman, out of Canada:

Normally when you talk about a finish it implies that it is a ‘finish’. For
floors that currently might mean something that has some sacrificial
durability and resists liquids, stains, etc. A 100 years ago in N.A. floors
were often untreated and swept with sand. Conventions change.

A lot of oils are used as finishes in woodworking for a variety of reasons.
One of the basic divisions is whether an oil can be classified as a ‘drying’
oil or an oil that forms a film. The chemistry is pretty interesting and is
subject to a lot of modifications. Linseed oil has been a predominant oil as
its been cheap and a byproduct of major industries. It is not a true ‘drying
oil’ and forms a soft film. This was ‘improved’ upon by heating and adding
heavy metals as driers. The predominant metal used is lead as well as
cadmium. This used to be marketed as a boiled linseed oil and typically now
is called a polymerized oil. There are products that polymerize without
heavy metals like the Tried and True but it’s a recipe that does not
disclose what is included and is expensive. Linseed oil also remains a food
source so is prone to mildew spotting in moist locations.

You can use any kind of oil on a floor. A traditional japanese floor washing
treatment was to use bath water with human oil. I’ve used safflower oil. It
is a question of what you want as a result. If somebody wants a ‘floor
finish’ then I can only recommend products that fulfill the criteria of what
they want.

The point in providing a specification is using a treatment that provides a
recognized degree of finish and durability without guesswork. Raw tung oil
is a ‘natural’ toxic material and that is part of why it is a durable
material. It is also the only true drying oil in its natural state available
that will provide a significantly durable alternative to polyurethane or
alkyd finishes.

In supplying floor finishers on projects the cost is about $50 per gallon
for raw tung oil which is about the best price I can get in Canada. As a raw
material its diluted with pure turpentine (less toxic than citrus) and so
averages about 30 per gallon. Its also available in larger quantities in the
US for about $20. The expense is small compared to the wood and labour cost
of a floor. Toxicity is initially voc (terpene) and then the setting of the
oil (about 7 days which is comparable to any poly finish).