Gum chemistry is simple and easy and Gloy

 In a message dated 19/03/2006 20:57:13 GMT Standard Time,
kthayer@pacifier.com writes:

I do agree with another statement in the above-referenced post, to 
the effect that knowing how the gum process works won't make anyone a 
better gum printer,

 On the contrary, understanding how things work gives a better understanding
of how they should be done.

 Again,  the principle of how gum dichromate works is simple.

 Long chain  molecules  of gums, with bits sticking out of the side.like a
ladder with a central upright,. are flexible; this flexibility makes the
substance soluble.

 The dichromate molecule is unstable,  atoms break off when they are exposed
to powerful energy such as UV light.. The atoms which break off join up the
rungs of the ladder of the gum making it inflexible. That inflexibility renders
the substance insoluble.

 The longer the exposure the more insoluble the substance becomes, i.e. less
contrast.  The more pigment that gets in the way of the UV light, the less
insoluble the substance becomes, i.e. more contrast.

 See my web site and the introductory chapters of any good A level chemistry
text book up the chapters on the structure of molecules and the periodic
table.

 As to PVA we have made a substitute for Gloy which gives multiple exposures
with acrylics..Knowing how it works helped us to do so.

 Terry
Received on Mon Mar 20 05:24:11 2006