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Pre finishing gold casting


#1

hello,

i’m getting my first 18k gold ring from the casting shop next week.
just a casting with no finishing work. the setting has a series of
domes going along the length of the band (is very contoured).

ive been reading that pre finishing these surfaces after filing, is
best done with natural bristle brushes & also the newer concept of
the 3m bristle brushes rather than abrasive paper so as to avoid
flat spots. do most goldsmiths now prefinish every surface with the
3m bristle brushes or is this just the way to go for highly curved
contoured pieces. if so, are they as good as each other as far as
results go, or are the 3m bristle brushes superior can a natural
bristle hand brush with polishing compound be used for prefinishing
(i’m thinking a big no).

sorry about these beginner questions & thanks for any replies & help
offered.

joel


#2
are the 3m bristle brushes superior can a natural bristle hand
brush with polishing compound be used for 

Joel, if you want a good polished finish on any metal, cast or not,
there are three steps - file, sand and polish, which has it’s own
steps involved. You’re not likely to get a good polish by going from
filing to a bristle brush - maybe with greystar or something, but
that’s awfully aggressive. The 3m brushes are nice - I don’t use them
a lot, but sometimes. What any jeweler will do is use the right tool
for the job, so whatever works for you is best. I use what we call
rubber wheels a lot, so I’m used to it - that’s what we call the
whole family of Cratex and Shofu and similar. Most 18kt is quite
soft, so you can have problems with faceting, but you can also
contour a lot on the polisher. In a nutshell, a bristle brush is
probably not going to get you a good polish from filing, unless
you’re using #6 files. You’ll have to work so hard it will probably
degrade the piece. And the 3m wheels are probably a good choice for
the sanding - not the only choice, but a good choice.

http://www.donivanandmaggiora.com


#3

Hey Joel, The first question to address is just how rough the surface
is. Are there file marks from carving wax or was it glass smooth b4
casting? 99.9% of the time it is easier to work in wax… get it
perfect!!! Saves on lost metal, casting weights, finishing time,etc.
etc. etc. I really try everything I can get my hands on( and have for
20 yrs)I own 3 sizes of the 3m brushes and for 10% of my projects I
break them out. Usually to work on and around heads and other small
contours. They don’t really do the trick for flat, large, sharp
surfaces. After tons of practice nearly everything is done with
silicon abrasives. ALWAYS DRAG, NEVER PUSH!!! Finish all crevices,
heads, holes, channels PERIOD b4 setting stones!!! It takes time yes,
but it separates you from others right away. For your first 18k piece
use what you Know works for 14k and it’s all good.

Rob Dufault

Joel, I Just realized that I didn’t make it clear that I was
speaking of pre-polish when I spoke of the silicone wheels. Final
polishing, is natural brushes and buffs, 3m green rouge (med cut)
leaves a rich color and cuts pretty fast, red… higher shine. For
smaller harder to reach places, anything from cotton shoe laces( or
string with polish, to polished out broken burs to burnish…
whatever fits and burnishes


#4

hello,

thanks to people for taking the time to reply. the setting i chose
may not be the easiest for first time finishing. it has 3 domes
going across the length of the wide band (parallel with the band). i
just got thinking that for a complete beginner getting a brush to
not take to much metal of the top of the dome whilst at the same
time sanding the recess could be a problem, or would the 3m brushes
not take to much off the ridges? ive been looking at the cratex
hand sanding sticks, both round & square, that i thought may conform
well to the peice ? also the 3m sanding sponge. also, you mentioned
dragging with the silicone rubber abrasives, is that always towards
you so you dont put to much weight on ?

thanks again
joel