Wayde Allen (wallen@boulder.nist.gov)
Fri, 16 Jul 1999 09:21:22 -0600 (MDT)
On Fri, 16 Jul 1999, Campos & Davis Photos wrote:
> We make lots of jam, but have never heard of sealing the lids with
> paraffin.
Actually, it isn't so much sealing the lid with paraffin wax as it is
making a lid out of paraffin wax. All that is done is to melt the
paraffin and pour it onto the surface of the jelly or jam in the jar. The
paraffin solidifies to form a cap that seals the jar. At this point a
metal lid is kind of optional.
> the back of paper negatives to make them more transparent. It is cheap and
> easy. It arrives as liquid in a bottle. One person on the list send a very
> detailed description of what the difference was but I cant remember it.
I think it was decided that the liquid you are talking about is what we
call mineral oil. Let's see, my dictionary says:
mineral oil - any oil found in the rock strata of the earth;
a) petroleum b) any of various colorless, tasteless oils
derived from petroleum and used as a laxative
paraffin - 1. a white, waxy, odorless, tasteless solid substance
consisting of a mixture of straight-chain, saturated
hydrocarbons: it is obtained chiefly from the distillation
of petroleum and is used for making candles, sealing
preserving jars, waterproofing paper, etc. 2. Chem. any
hydrocarbon of the methane series 3. [Brit.] same as
kerosene
kerosene - a thin oil distilled from petroleum or shale oil, used as a
fuel, solvent, illuminant, etc.; coal oil: also, esp. in
scientific and industrial usage
These are all definitely related and obviously not mutually exclusive
terms.
> I cant think how you could be using this to seal jam jars, and also what
> is the purpose of sealing them? The high sugar content of jam ensures
> the jam stays preserved for a year or more.
That is true, however the sugar is hygroscopic and will absorb moisture
from the air. A little water, sugar, and the added food value of the
fruit and pectin makes a nice culture medium for mold growth on the
exposed surface even though the bulk of the jelly is relatively well
preserved.
- Wayde
(wallen@boulder.nist.gov)
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