From: Rod Fleming (rodfleming@sol.co.uk)
Date: 05/14/00-04:06:51 AM Z
Hi
I actually thought we had moved on from here, but it seems not.
From: "Richard Knoppow" <dickburk@ix.netcom.com>
To: <alt-photo-process-l@skyway.usask.ca>
Sent: Sunday, May 14, 2000 12:58
Subject: Re: Ferrotyping Alt. Prints.
> I have metal ferrotype tins which have a dull surface and make dull
looking
> prints. They were that way when new. Good ferrotype plates are the
> brightest polished chrome, not the duller type which seems to be widely
sold.
This is at the heart of Mr Knoppow's fundamental misunderstanding of the
process. In ferrotyping on enamel tins the glaze is produced by the surface
of the wax which is polished on to the tin prior to its use. Whether the
surface of the enamel paint itself is glossy or not before preparation is
irrelevant- the question is of how glossy the surface is _after_ it has been
wax polished. Indeed the surface of the enamel plate is supposed to be dull,
for it is this dullness which provides the "tooth" which allows the wax
coating to adhere evenly!
Wax has the property that it can be polished to a very high gloss, and the
point made, but again misunderstood by Mr Knoppow, is that the gelatin
surface of the print exactly replicates the surface it is dried in contact
with. The wax surface can be made brilliantly glossy, homegenous and is
totally impervious to water.
The production of enamel ferrotype tins utilises the surface tension of the
wet enamel, which tends to smooth out underlying defects. This effect
combines with the relatively thick paint coat to produce tins with a very
smooth, though not glossy, surface, very cheaply.
By comparison with enamel chromium plate is very thin. Contrary to the
surface tension effect which is a benefit in enamelling, electroplating
tends to deposit more on high points- ie, it tends to make an uneven surface
more so. Therefore chrome relies entirely for its smoothness on the
smoothness of the underlying metal, meaning that the substrate has to be
polished to a very high degree _before_ plating.
It should be obvious that the extra work involved in manufacturing the
chrome plates, added to the expense of the plating itself, means that they
are much more expensive than enamel finished plates. However in this
context, "more expensive" does not translate as "better".
Furthermore, chromium plate itself is not impervious to water, which is why
it is always, when plated onto ferrous metals, used in conjunction with
intermediate platings of copper and nickel- the copper improves the adhesion
of the nickel, and the nickel is more impervious to water than chromium.
The chrome plate alone cannot achieve the same brilliant gloss of a waxed
surface, although it is very good indeed- much better than contemporary RC
"gloss". However, the production of said waxed surface is hard,
time-consuming and most importantly, skilled work. It is possible that this
gives a clue to the reason why Mr Knoppow has not had success with the
enamel tins.
It should be appreciated that "advances" in photo techniques are powered
almost entirely by the demands of the photo-finishing business, and glazing
on chrome, which will produce an excellent glaze with simple cleaning, is
easier, quicker, and requires much less training than doing the same job on
enamel ferrotype tins. So chrome is cheaper per print than enamel, even
though the tins are more expensive. Chrome even lends itself to
semi-automated processes, cutting manual work still further. And this is why
the older method was superseded, even though it was capable of a better
finish.
> I should not have to point out to this group that the term "ferrotype"
> has another, much older, meaning refering to a direct positive process
> similar to the "tintype".
I wonder indeed why you bother, since the "ferrotype" you here refer to is
akin to the ambrotype, and is totally different from anything which has
hitherto been discussed in this thread. I think we all knew what we were
talking about- I know I do.
I am also confident that others must be getting tired of this somewhat
esoteric discussion, so if Mr Knoppow is still unclear on any details, he
may contact me off-list where the discussion can be continued in private.
Rod
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