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Sandblasting - type and size grit


#1

hi everyone, i was happy to find your forum, and hope you can help me.
what type and size grit abrasive is best to produce a very matte
surface on 18kt gold. i do have the equipment but haven’t used it in
years, i hope to get back into making my own jewelry again. also what
psi should i use? thank you sherrie


#2

Hi Sherrie, I’ tried a lot of methods but the " heaviest" results I’
have got using :

  1. common sea-sand (you have to wash it in clear water and dry very
    well)

  2. gross corundum sand (not spheres but irregular one, because
    spheres make the surfaces too smooth) I hope it will be useful.

"LABORATORIO GUS" di Claudio Gussini

#3

Sherrie,

I would recommend that you use glass beads rather than sand. You can
get these from industrial sandblasting supply companies (yellow
pages, Thomas Register — usually 50 lb bags for about $30.00) and
many of the jewelry suppliers should carry them (much more expensive
but in smaller quantities). I use beads on the art castings I do and
my wife (the jeweler) and I use the same beads on much of the jewelry
to clean off the investment. When I got the last 500 lbs of beads I
say that they had 18 different sizes and I got #10 which leaves a
semi mat finish. (#1 is the biggest and #18 is like dust).

Hopes this helps a bit.
John


#4

Course grain materials, especially the corundum mentioned above, will
erode metal from the piece, so if you have fine detail be careful.
The beads and any heavily washed (meaning "washed in the ocean surf
or in a river so the sand grain is smoothed or rounded rather than
sharp edged) do not erode the target material as much but some
erosion will still occur. The sand would possibly be easier to come
by but I would suggest that you try different blasting media to get
one you like because they do make different textures.

John


#5

hi john and all, john did you try the #18 glass beads? what was the
result? thanks for your help. i haven’t tried the glass beads.


#6

hi gus and all, i think i did use corundum and it seems it was 200
grit. i really need a very light and very matte finish that’s easily
removed. I wonder if there’s any coatings i could use as well. every
where i look i see matte finishes in jewelry. where can i buy
corundum? would a lower psi,make the finish easier to remove? thanks
sherrie


#7

Sherrie,

In your other post you asked if I tried the #18 beads. No I didn’t,
I just was looking at samples in some bottles so folks could decide
which grade they wanted. # 18 was very fine however.

Lowering the air pressure will usually make a “lighter” not so deep
matte surface so it would most likely easier to remove. Question,
why are you trying to get a matte finish that you are going to
remove?? Are you removing it from areas you want polished and
leaving matte in the areas you want it? Have you thought about using
a mask to keep bright areas bright? Also, using “air brush” or “air
pen” blasting units would allow you far greater control over what is
and is not getting matted. Paschaa (spelling is not correct here)
air brush company makes air brush blasters for very fine, detailed
work. I think they are about $80. Douglas and Sturgess
(800-278-7883) has them and I think the blasting media too. Corundum
is usually available from any lapidary supplier.

John Dach
MidLife Crisis Enterprises
Cynthia Thomas Designs
Cynthia’s sculptures are at: http://www.mlce.net
Maiden Metals,


#8

Many countries have legislation in place forbidding commercial
operators from using SAND for GRITblasting operations. By sand is
meant beach or river sand or anything else containing appreciable
quantities of silica. The reason is of course that the dust is
especially dangerous to the lungs. Best always to use materials
specifically sold for gritblasting. Incidentally, glass beads do not
contain much in the way of silica (SiO2) … it is combined with
metals during the glassmaking process. Be aware, as always, that all
dusts should be avoided as much as possible and regarded as an
inhalation hazard. Of course, if you are not operating commercially
then what you use is a matter of concern only to you and your lungs.
And your family.

Kevin  UK

#9

Hi John and all, I’ve been making very small charms in great detail.
Sometimes the pieces are only 5-10 mm. I so enjoy makings things
smaller, I’ll have to move over to nanotechnology pretty soon. I
think the pen eraser will work well.

I didn’t find corundum powder in several suppliers. Where should I
look?. Also, usually its easier for me to remove the finish because
of the size. I’ll try different psi settings. I’m very interested in
what everyone else uses and their experiences with sandblasting.
Thak you for all your help. Sherrie