# Fume Hood Window



## Noxx (Oct 27, 2011)

Hey,


I'm designing a fume hood which will be 5 or 6 feet long. Now, I decided to use Lexan (polycarbonate) instead of acrylic. I can get 4'x8' sheets of a thickness of 1/8'' and 1/4''. 

They are $171 & $313 respectively. What would be best for my application ? I don't want to sheet to flex due to negative pressure. 

I know that Polycarbonate is sometimes not recommended but how well does it resist to non-solvent chemicals ?


Thank you


----------



## Geo (Oct 27, 2011)

from wiki. hope it helps.

Polycarbonates, known by the trademarked names Lexan, Makrolon, Makroclear and others, are a particular group of thermoplastic polymers. They are easily worked, moulded, and thermoformed. Because of these properties, polycarbonates find many applications. Polycarbonates do not have a unique plastic identification code and are identified as Other, 7.

Chemical Resistance 
Acids – concentrated Poor 
Acids – dilute Good 
Alcohols Good 
Alkalis Good-Poor 
Aromatic hydrocarbons Poor 
Greases & Oils Good-fair 
Halogenated Hydrocarbons Good-poor 
Halogens Poor 
Ketones Poor


----------



## 4metals (Oct 27, 2011)

One way to get away with the thinnest (and cheapest) sheet is to contact cement it to a sheet of plywood. Just build it of plywood with the inner sides of the thin sheet goods.

 sorry just saw the subject "fume hood window" loose the plywood backing idea.


----------



## Harold_V (Oct 28, 2011)

The loading on that surface area, even with just a half pound pressure difference, is going to be severe. I'm not convinced even ¼" material would resist bowing, especially if it was warmed slightly. 

I used a piece of ¼" tempered glass for my window, a decision I never regretted. 

Harold


----------



## gold4mike (Oct 28, 2011)

I used 1/4" Lexan and it still bows a bit when I seal up too much of the opening. I'm using it to span a 30 inch opening. 

I use a discarded furnace blower and wired up the high side. I will probably buy install a rectifier on it soon to gain some control over the draw.


----------



## Noxx (Oct 29, 2011)

Thanks Harold. 

I did not consider tempered glass because I thought that I could not find it locally. It is, however, not true.

I also want to share this company I found; http://www.onedayglass.com

They can cut tempered glass to specific sizes and drill holes for very cheap. They also ship in CONUS.


----------



## Claudie (Oct 29, 2011)

I get my tempered glass from discarded entertainment center doors & shelves. The glass from cooking ovens is also tempered. Many storm doors have tempered glass windows in them. Refrigerator shelves are also tempered glass. Tempered glass is everywhere.... :|


----------



## Harold_V (Oct 30, 2011)

Claudie said:


> I get my tempered glass from discarded entertainment center doors & shelves. The glass from cooking ovens is also tempered. Many storm doors have tempered glass windows in them. Refrigerator shelves are also tempered glass. Tempered glass is everywhere.... :|


Shower doors are tempered glass, too. (That's assuming they're not plastic)

Harold


----------



## Harold_V (Oct 30, 2011)

Noxx said:


> Thanks Harold.
> 
> I did not consider tempered glass because I thought that I could not find it locally. It is, however, not true.


The one real negative is that ¼" (6 mm) glass weighs about 3½ pounds/square foot. It can be a handful to handle. Mine was much smaller, so it wasn't an issue. 

Harold


----------



## 4metals (Oct 30, 2011)

If you know any woodworkers you can use a rail and style panel door frame to frame some cheap plexiglass. 

If you know someone with the router bits to cut the pieces it can be very economical.


----------

