<VV> Curved float glass, no Corvair

[James Davis]

Float glass is cooled very slowly; then cut (scored and broken) in to 
specific sized based on the intended use.  Float glass pieces for 
windshield are normally 8 x 4 foot sheets; for house windows it is 8 x 
12.  Standard shipping sizes are 12 by 20 in packs of 50 lites.  Typical 
float is 13 foot wide  There is a float plant in Japan that has a ten meter 
wide float. As edge of the sheet is pinched by the pull rollers, it is not 
optically good.  About 6 inches on each edge is removed at the plant    If 
curved glass is needed it the float glass is heated to the sag point then 
placed on a mold and allowed to air cool, tempering the glass.  The glass 
is cut to the mold by a hot wire cutter, while it is at the sag point, 
which smooths the edges.  There are two different molds for sandwich curved 
glass, inner and outer. The sandwich glass is assembled with the glass 
cold, then heated to the plastic point of the center filler in an autoclave 
or vacuum chamber to remove all air between the glass.  Flat side lites are 
usually cut to the right shape, again with a hot wire, then tempered in 
tempering oven, hanging vertical.  If you look carefully, you can see the 
clamp dimples in the lower edge of the glass.  If the side and back lites 
are curved, it is done by molding.
As an item of interest: float glass furnaces take 30 days to start and then 
operate for 10 year continuously.  The line is  shut down and after a 60 
day cooling period the furnace is broken up  The entire line 
replaced/rebuild, furnace replaced and then the line is restarted.  Bulk 
glass is usually shipped is special bottomless trucks.  The trucks back 
over the glass pack and hydraulics lift the glass into the trailer where it 
is clamped in place against one side.  A safety floor is then put into the 
trailer under the glass to protect it from road damage    When I lived in 
Shreveport, LA,  Libby glass had a fire in the plant necessitation furnace 
shutdown.  It took one year to restart the plant.  I watched 20 guys in 
space suits with jack hammers trying to bust up the 34 x 8  foot glass 
puddle left in the floor of the furnace.  It make a lasting memory.
Jim Davis


At 12:17 PM 5/18/2005, N. Joseph Potts wrote:
>I'm trying to figure out how you make a curved piece of glass by floating it
>on some liquid.
>
>Joe Potts
>Miami, Florida USA