How to smooth a rough glass edges into a sparkling smooth surface.

Is it possible to cut glass so straight and flat that when you slide the glass in
parallel that you cannot see the seems. I am building a magician's prop
and I need to cut glass so that when I slide them pass each other the
seems will fit so precisely that they can become invisible. The Japanese
have done it. Also, I've separated glass into two pieces and join
them temporary and the seems have disappeared. The trick now is to
be able to slide them in parallel without showing the seems. This means
that to two glass will have to extremely straight and smooth.

What kinds of tools can I use to lap the edge of the glass to get it so
smooth and flat that the surface of the edge of the glass is as smooth the
face of the glass itself?

Thanks

"Sam Nickaby" wrote in message
. com...
Is it possible to cut glass so straight and flat that when you slide the
glass in
parallel that you cannot see the seems. I am building a magician's prop
and I need to cut glass so that when I slide them pass each other the
seems will fit so precisely that they can become invisible. The Japanese
have done it. Also, I've separated glass into two pieces and join
them temporary and the seems have disappeared. The trick now is to
be able to slide them in parallel without showing the seems. This means
that to two glass will have to extremely straight and smooth.

What kinds of tools can I use to lap the edge of the glass to get it so
smooth and flat that the surface of the edge of the glass is as smooth the
face of the glass itself?

Thanks

Lots of variables here.

How big are the pieces? How thick is the glass? Just POG (plain old
glass)? No patterns or textures? Clear in color?

This glass has to sit edge to edge in a vertical position and the top piece
has to slide on the bottom pieces' top edge?


If you are talking about pieces of glass that is the size of your hand,
there are several people on this glass forum who do beveling and could do it
for you. Any bigger, and I think you'd better be looking for someone who
bevels mirrors or table tops.

It is possible to grind the edges of glass perfectly straight..well, within
reasonable tolerances, (a few .001"), and to polish those edges as smooth
as the face of the glass.

However, it seems to me that the edges would have to have some small radius
to them, otherwise you'd be succeptible to chipping the edges and/or
cutting yourself. And that small radius might be visible, even if it were
polished, too.

Any chance you could post a link to a photo of this prop?

"Sam Nickaby" wrote in message
. com...
Is it possible to cut glass so straight and flat that when you slide the
glass in
parallel that you cannot see the seems.

Then he said ---
The Japanese
have done it.

So the answer must be, "Yes, it is possible."

What kinds of tools can I use to lap the edge of the glass to get it so
smooth and flat that the surface of the edge of the glass is as smooth the
face of the glass itself?

It's called a "flat lap", and if you have to do it by hand, you'll regret
trying. First, you'll need a lap plate at least as wide as the length of
the edge you're lapping. Second, you'll need to perfect the skill of using
Newtonian Ring patterns to determine flatness (which will be very hard,
since you're looking through the whole width of the glass).

Then, of course, unless you're grinding two flats to one-another, you'll
need a standard flat against which to gauge yours.

This doesn't sound like a fun exercise. I've ground flats for diagonal
mirrors for telescopes -- it's a jitsy, itchy, long, frustrating process
until you're quite skilled at it. Grinding a couple of flats won't get you
up to "skilled", just down to "very frustrated".

And you'll never make the seam disappear entirely.

LLoyd

Sam Nickaby wrote:
Is it possible to cut glass so straight and flat that when you slide the glass in
parallel that you cannot see the seems. I am building a magician's prop
and I need to cut glass so that when I slide them pass each other the
seems will fit so precisely that they can become invisible. The Japanese
have done it. Also, I've separated glass into two pieces and join
them temporary and the seems have disappeared. The trick now is to
be able to slide them in parallel without showing the seems. This means
that to two glass will have to extremely straight and smooth.

What kinds of tools can I use to lap the edge of the glass to get it so
smooth and flat that the surface of the edge of the glass is as smooth the
face of the glass itself?

Thanks

The 2 pieces will have to fit together so well that there will be no
gap, and therefore no air in the gap to cause reflection and
refraction. For a sliding surface, that level of straightness will have
to be maintained for the length of the seam.

Perhaps you can lap the 2 pieces against each other?

D

wrote: The 2 pieces will have to fit together so
well that there will be no gap, and therefore no air in the gap to cause
reflection and refraction. (clip)
^^^^^^^^^^^^^^^^^
How about introducing a drop of liquid with the same index of refraction as
the glass?

Sam

Not sure I understand what you are doing but the usual method that
optics people use to hide interfaces is oil/glue of the same refractive
index as the glass. Doesn't take much if you are using float glass,
since it's already nearly perfectly flat. Mineralogists use oil to
measure refractive indexes so you might ask around in that part of the web.

Water works pretty well for a lot of applications, like the old
disappearing quarter illusion where the glass circle sticks to the
bottom of the glass by surface tension and is virtually invisible. I'd
try it first, since it's cheap and readily available. If you're not
doing close up work, you can be a lot less picky. A couple feet of
distance will hide a lot of mismatches.

A few distracting parallels will help hid things too. The eye tends to
ignore repeating patterns (probably part of our rodent ancestors
filtering out the leaves to see the predators), so you can hide a join
in plain sight if it's part of a pattern.

Sounds like an interesting project.

Jim

Take it from a guy that does optical glass work that you'll never get a fit
good enough that you won't see the gap except at a very narrow angle.
However, you can put some oil, cooking oil or such, on the joint and it will
go away on you real easy. You don't need much oil to do the job if your
glass is good and flat but you can't touch that surface with anything else
or you will wick up some of the oil and thus have a problem
You do need to grind and polish the edges flat to at least 1/4 wave of flat
and parallel to each other or the effect may not happen. You also need to
keep the corners of the edges as square as you can which means that you're
going to have to handle those edges very carefully as any chips will happen
with a mild touch with something hard and the chips will show badly if not
destroy the glass.
Don't even plan on hand edging the glass but rather do it on a machine so
that the long length will be flat. I'll note that large diameter flats (6"
and larger) tend to be rather expensive as they are flat over the whole area
and you're going to be even more expensive because the work won't be common
work that is done by the shop. You might want to specify that they do a
dozen of them at a time which will bring the cost of each piece down by that
amount. Also note that an optical shop will normally chamfer an edge so
you will have to specify that the edges be fully sharp and this will be
helped by doing a bunch of the surfaces together.

--
Why do penguins walk so far to get to their nesting grounds?

"Sam Nickaby" wrote in message
. com...
Is it possible to cut glass so straight and flat that when you slide the
glass in
parallel that you cannot see the seems. I am building a magician's prop
and I need to cut glass so that when I slide them pass each other the
seems will fit so precisely that they can become invisible. The Japanese
have done it. Also, I've separated glass into two pieces and join
them temporary and the seems have disappeared. The trick now is to
be able to slide them in parallel without showing the seems. This means
that to two glass will have to extremely straight and smooth.

What kinds of tools can I use to lap the edge of the glass to get it so
smooth and flat that the surface of the edge of the glass is as smooth the
face of the glass itself?

Thanks



Ahh this is a much bigger trick than the trick you'll be using this for
is my guess.

--
JK Sinrod
www.SinrodStudios.com
www.MyConeyIslandMemories.com

"glassman" wrote in message
...

"Sam Nickaby" wrote in message
. com...
Is it possible to cut glass so straight and flat that when you slide the
glass in
parallel that you cannot see the seems. I am building a magician's prop
and I need to cut glass so that when I slide them pass each other the
seems will fit so precisely that they can become invisible. The Japanese
have done it. Also, I've separated glass into two pieces and join
them temporary and the seems have disappeared. The trick now is to
be able to slide them in parallel without showing the seems. This means
that to two glass will have to extremely straight and smooth.

What kinds of tools can I use to lap the edge of the glass to get it so
smooth and flat that the surface of the edge of the glass is as smooth
the
face of the glass itself?

Thanks



Ahh this is a much bigger trick than the trick you'll be using this for
is my guess.

--
I'm thinking I know somebody who is just itching to sell this guy a wet belt
sander. Wouldn't that do the trick? :)

One trick from woodworking (or somewhere... I can't recall where it is
that I used this) is to grind the two pieces against each other. No
need for a reference "straight" piece -- the two will self-correct for
any non-straightness.

But it sounds like that would be awfully hard to do with glass by hand.