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Agate carving and polishing


#1

Dear Orchidians,

I need some advice on carving and polishing agate. My experience only
goes as far cutting and polishing cabochons. I find that agates are
easy to polish as long as there are no flat spots or unseen
scratches. I have an agate with patterns that would be lost if I cut
a round or oval shape to start. I guess you could call it a free
form, even though it looks more like a chili pepper. It requires
concave cuts and polishing that I can’t do on my single 6 inch
expandable drum and silicon carbide sanding belts. I have done
almost all of my lapidary work on this one tool. Progress has been
painfully slow trying to remove the remaining saw marks on the right
side while trying to create a very gradual convex surface on the
face. I don’t want to flat lap it and create a hard line where curve
meets flat. I have the Foredom flex shaft with small sanding drums,
some adhesive-backed diamond papers, polishing pads, etc., but I
don’t know what to use. I will gladly follow any instructions given
to finish this stone for my wife. The object is to not lose anymore
color at each end of the stone and to get the best polish possible,
even if I have to spend hours by hand sanding and polishing. Could
someone please help me or direct me on what I need to do. This is one
stone that I will likely never see another quite as beautiful.

Thank you,

Jeff


#2

Jeff

That is truly a remarkable stone and as a lapidary myself,
congratulations on extracting it.

Let me also start by saying, don’t touch anything until we have all
weighed in on an approach. Pick what makes the best sense to you and
go for it, on a practice piece. You will be learning a new way of
working stone and it will take practice to get acceptable results,
just like when you started with the wheels.

As you have a flex shaft, I have used felt fobs to polish such
items, though I have not tried creating a concave to any great
degree. Substances I have used are loose graded carbide grit
impregnated onto a fob and I have also used diamond paste on a fob.
As you would suspect both will fling off pretty quick if you get to
much speed on your flex shaft or not work well if you go to slow.
Follow the same grit you would use in normal progression with the
carbide grit if you go that way. The diamond will run finer to obtain
the same result. Like when you put on a new 600 belt and work it down
for use, on diamond this seems to be around 1000 or 1200 for me. The
felt pieces come in many shapes and you should be able to find one
in a shape for each aspect of merging or blending the curves. My most
used is the bullet shaped buff. Get those which are densely packed,
they hold up better and hold the grit better. With the carbide grits
I use a mist to keep it damp, on diamond I use a little mineral oil.

The usual polishing agents work with the felts, cerium, Linde or any
other you may be used to using for agate, speed is ok at this point.
With the felts, I use film canisters to put them in to keep the grits
separate, and as always wash between grits, you, the stone, and the
handpeice.

I have had a problem with breakage when dopping unusual shapes that
are thin. You might try this, I dop to a plate of copper or brass
after roughing and the first sanding. I clamp the plate to the bench
to hold the work and then move the hand piece around using my other
hand as a steady, or sometimes I use a wood dowel with a rubber tip
when using bits. When you are done, put the piece back on your hot
plate until the wax melts slip a tooth pick under it, wipe with a
paper towel, and finish your clean up with alcohol to get the rest of
the wax off. I haven’t broken any since I started doing it this way.

Good luck with your stone.
Terry


#3

There are several great books on carving. Tom harmon, henry hunt,
work with montana agates.

Myself, I carve jade and agates, have just started a 550 gram smokey
quartz, 7 inches long, the piece is facet grade, and I did not want
to do a large conventional faceted stone

the best way to learn to carve - take a scrap piece of material,
similar to the actual stone you want to finish, and have at it, play
with it, work it, see what you can make it do.

as you grind, work symmetrically, avoid large pits. I recommend
diamond points from Lasco, they will fit your flex shaft. also, use
1200 and 14,000 diamond paste on a hard pad for polishing, avoid
heat buildup on agate or it will fracture.

keep in mind: you know those fantastic oriental carvings from
1700-1920p ad? they were done with wire, sand, and alot of patience.
So, your 6" machine will work well.

Mark Zirinsky, Denver


#4
I need some advice on carving and polishing agate. My experience
only goes as far cutting and polishing cabochons. 

First, look into the Crystalite line of produts:

http://www.crystalite.com

You may be able to find similar things in different brands. They used
to make a “Full Circle Wheel”, which is a 4" x 1/4" wheel with a
radiused edge. They make similar that is flex-shaft sized, and many
other things useful for carving. I stopped doing carving, now, but I
used to use a Cool Whip container 2/3 full of water with a flex shaft
for carving - crude but effective. I say Cool Whip, or similar,
because of the flexible sides. Reaching into a glass bowl is way more
difficult. For polishing, get some diamond paste

  • 180, 400, 600, 1200, 14,000 and 50,000 - you don’t need all of
    them, but you will if you carve much. At least 600, 1200 and 14,000.
    I like Linde A for polish

  • I did a lot of rock crystal. You can put that on anything porous
    for sanding. I used wooden wheels (homemade), dowels, toothpicks, or
    you can buy plain disks. What you are doing is no different than
    standard cabbing, you just need the right shaped tools to get the
    contours.

http://www.donivanandmaggiora.com


#5

Eish, Eish, Jeff, That has got to be the most beautiful agate I have
ever seen. I could do some things with that! Is that a one off or is
there more available?

Best advice I could give is to use wooden dowel sticks, charged with
the appropriate cutting compound 1200 grit, 14000 50,000 etc.

You buy the round dowel sticks at the hardware store.Cut them into
’polony’ slices of various lengths.

Drill a hole into the center and glue a shaft into the ‘more or less
center’. Then you put the shaft into your hanging motor or drill
press and true it up using a file or graver so they run smooth. You
’lathe’ it to the required shape That why I said more or less
center.

Then you take the appropriate diamond grit and mix it with olive
oil, WD 40 or butter or axle grease, for that matter, and you smear
the compound on the prepared wood piece…You recharge the wood as you
go along. I use 220, 1200 and 50000 as I remove prior scratches.

Also, I cut strips of the appropriate wet or dry sand paper ( the
black corundum stuff) and with my sanding mandrill, ( hanging motor)
I dip it into a bowl of water and sand my piece down. I know, it
sprays water every where but it works very well, until I get to the
’wooden’ stage of polishing. So I would wet the sanding mandrill,l
then work the stone piece for a little while, then tear the worn
piece of sandpaper off and wet it again and continue. If you use
Carborundum 1200 without water, it starts to polish the stone. This
you want to avoid. It causes an uneven surface when the final
polishing stage is reached. I use this method mostly with 220 and
1200 grit. I spray the hand piece with WD 40 to stop rust.

Indeed, if I have a large piece of quartz, say + 50mm, and I want to
finish a smooth curve, I take cotton cloth ( like an old teeshirt),
cut it into strips and impregnate it with the right grit,( that is,
smear it with my grease and compound) put it in my drill press in a
large split mandrill, ( 6mm thick, cut with a small hacksaw down the
center), set the speed to about 300rpm It is a bit bumpy at first,
but
it mellows in a short time.

If you have done the early grinding carefully the prepolish feels
very sensual.Smooth and satin like, but not glossy. LOOK with an
Optivisor carefully for deeper scratches Trying to polish a badly
prepared surface is a schlep and wastes time.

One thing to watch out for is that if you use a very course grit at
first, it is more likely to make finishing off more difficult.After a
Mizzy heatless wheel, or a green grinding wheel, I go to 220 grit,
and I spent a long time there.I go over and over the surface,
checking with a loupe to see that every last grinding wheel mark is
gone— Ergo, a finer grit takes more time, but it easier to get to a
high polish in a shorter time.And polishing always takes the longest
time.

I purchase diamond powder at Crystalite, but there are many other
suppliers. A bit rambling, I know, but if you need any pictures, you
are welcome.

Cheers Hans Meevis
http://www.meevis.com


#6

Nice stone. Try a Google search using, “polishing fire agate” or
"carving agate". I know your piece is not fire agate, but the methods
are the same.

Will E.


#7

Hans says essentially the same thing today. The original post was
What about carving? Generically, and it opens up this whole world.
But if you just want to polish your one (gorgeous!) agate without
spending $1000, you can just do it the old fashioned way, get some
sandpaper and do it by hand. It won’t take that long. Use a wood
block or dowel or whatever suits behind it for crisp edges, or just
your fingers where that’s better. Use grit, as Hans says, or
carborundum sandpaper, and keep it wet. People (me included) tend to
forget there wasn’t always electricity, and they got by just
fine…

http://www.donivanandmaggiora.com


#8

There are several options that will work reasonably from where you
are starting. I am assuming that you just want to finish this stone
not get in to carving in general. Also I am assuming from your
picture that you have shaped the stone as you want it and don’t want
to continue grinding it out any more. If you do want to shape it more
the Lasco burrs are a good way to go.

You said you have some diamond paper but didn’t say what grits you
have. If you have 220, 600, and 1200 that should be good enough
although a 3000 to 14000 would probably help. Hand sanding with just
one stone isn’t that slow, it is not as fast as your cabbing machine
but not so slow as to be unacceptable. Just keep the stone and the
paper wet and check VERY carefully to make sure you have eliminated
all the scratches before you go on to the next grit.

If you want to try your flex shaft there are two different wheel
sets that will work well for what you want.

First, Diamond Pacific has a set on points called Nova Points. They
are made of the same diamond and rubber mixture that they use on
their cabbing machines like the Genie. For what you are asking, I
would suggest their N2L series and 280, 600, 1200, and 3000 grit
points. Keep everything wet and just consider them to be small
cabbing wheels.

A second way to go is with Eastwind’s small diamond disks. They have
a set of diamond PSA backed disks in 1/2, 1, and 1-1/2 inch sizes and
small rubber mounting wheels for them. I would recommend the 1 inch
size and 220, 600, 1200, and 3000 grit disks. Again keep everything
wet. Crystalite and Ameritool both have similar products but I like
the Eastwind’s best.

I think the Diamond Pacific wheels are a little easier to use but
both work well and it just may be that i am more used to the Nova
points.

Polish with what ever you are currently using. Most polishing wheels
have enough give in them to allow access to the amount of concave you
show in your picture.

If you can’t reach the bottom of the concave with your setup, get
some scrap shoe leather and cut a 1 inch leather disk, or get a 1
inch hard felt wheel and mount it on a mandrel. Use your polish of
choice, cerium oxide, aluminum oxide, or diamond will all work but if
you are happy with what ever you are using, there is no reason to
change unless you just want to try something new.

If you want to get into carving, and I recommend doing so, read all
the advise you are getting here and see if some of the options seem
like a place you want to start. Try any, or several of them and see
what results you get. Then come back and ask more questions, you will
probably get more answers than you know what to do with. :wink:

Dick Friesen


#9
Hans says essentially the same thing today. The original post was
What about carving? Generically, and it opens up this whole world.
But if you just want to polish your one (gorgeous!) agate without
spending $1000, you can just do it the old fashioned way, get some
sandpaper and do it by hand. It won't take that long. Use a wood
block or dowel or whatever suits behind it for crisp edges, or just
your fingers where that's better. Use grit, as Hans says, or
carborundum sandpaper, and keep it wet. People (me included) tend
to forget there wasn't always electricity, and they got by just
fine.... 

If you decide to do it by hand, you might want to consider the new 3M
diamond Microfinishing Film that can be used wet or dry. The
advantage of these new abrasives are that they are very speedy and
you will be able to use the same strips again for other projects.
Note that you can get an assortment pack of 7 X 1 strips–
http://tinyurl.com/ycbopr , PSA, backing (). Also note that this
assortment pack used to have just 4 grades and now has 6 grades
ranging from 9 to 125 micron (130 to 1800 grit).

Michael McKinnon
McKinnon Global
Fine Jewelry & Creative Supplies
1313 5th Street SE
Minneapolis, MN 55414
www.mckinnonglobal.com