Film-Tech Forum ARCHIVE: Port Glass recommendations in the UK?

This is topic Port Glass recommendations in the UK? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Amanda Mundin (Member # 3386) on 05-11-2006, 05:07 AM:

Does anyone have recommendations as to where to get good port glass in the UK?
I have read that they should be optical quality with anti-reflective coatings, is this correct?
Also what thickness of glass would anyone recommend?

Posted by Pete Naples (Member # 761) on 05-11-2006, 06:56 AM:

Amanda,

You want Pyran glass, this is optically excellent, anti-reflective, reduces sound transmission, satisfies the requirements for fire retardance and comes ready glazed in a frame unit, which can be easily removed to allow for cleaning and for us poor engineers to get mic cables into the theatre. These are fairly standard in new builds and refurbs, remember practically anything you do to the building will have to comply with the latest regs.

IIRC it comes in two standard sizes, although others can be made to order, at addistional cost.

Out office would be happy to cost it up for you [Wink]

Posted by Amanda Mundin (Member # 3386) on 05-11-2006, 07:11 AM:

What are opinions on using 2 panes of glass instead of 1?
Does 1 pane reduce projection noise sufficiently?
Does 2 panes start to introduce other problems like less light transmission and optical aberrations?

Posted by Dave Macaulay (Member # 813) on 05-11-2006, 09:47 AM:

Sound transmission is reduced with 2 panes. If you use optical clear coated glass, image degradation is negligible. The 2 panes should be angled vs the projection angle and each other to avoid any ghost images on screen.
One pane may be fine, thicker glass gives better sound isolation but noise will get through. The projection noise is usually not a big problem, but people talking in the booth may be clearly audible in the theatre... you don't want to discuss the patrons very loudly for sure!

Posted by Brian Guckian (Member # 1678) on 05-12-2006, 08:37 AM:

Here's a good tip...use rubber gasketing between the glass and the frames as well, and sound absorbing material in the space between panes if you go for two panes...

I worked in a theatre years ago where we did everything to the letter; twin panes, correctly angled, optical glass, you name it! BUT...the sound still got through. In the end we saw there was a hard bond between the glass and the wooden porthole frames, so vibrations from the glass were being passed through the frames and out the other side. And the space between the frames was lined with light-absorbing but not sound-absorbing material.

Our ports were also unavoidably big, because we had to accommodate three machines in tight space...so another requirement is to make the ports as small as possible.

You can buy pre-assembled portholes complete with frames, glass, cable pass-throughs and double-pane options. Talk to your projection equipment supplier...you have some very good ones there in the UK [thumbsup]

Posted by Ken McFall (Member # 845) on 05-12-2006, 05:59 PM:

and DON'T use georgian wired glass as was recomended by an installer who posts on this site!!!

SAD but true!

One other thing to bear in mind.
Where possible keep the port glass as small as practical and SEPERATE from the view port. The glass should be on the inside of the projection room to keep it small. Large single ports on the inside of the auditorium wall make it very difficult to focus as you are looking thru the image on the port glass. Smaller poprts also reduce the amout of stray light passing into the auditorium.

Most people consider the cost of port glass to be way over the top but it's importance cannot be over stressed. Ports tend to be very close to the rear seats so stray light and sound can be a real problem.

So do the job right..... and do it once.

Posted by Rob Younger (Member # 1770) on 05-15-2006, 02:56 PM:

Hi Amanda,
The glass that Pete has mentioned is what we were talking about last week. This would be good - and available from your favourite dealer!!!

Rob