vacuum – Fall River Editions

I’ve finally finished building a new vacuum frame. It replaces one I built a few years ago which used a commercially available plastic film called Kreen. I ran into too much variability in the UV density of that product and decided I needed to begin using a glass cover over the negative and paper.Here is the new frame with the UV exposure unit behind it. The frame rolls out from under the bulbs for access.

Finished vacuum frame in front of the exposure unit.

I built this unit over the existing frame using the original 3/4″ plywood as a base. The new frame is 1″ x 3″ select pine and the pieces measure 40″ (front and back) and 30″ sides.

Here, I am pre-drilling holes for mounting the aluminum strips which will hold the Neoprene sheet in place. It was quite a project drilling then countersinking the aluminum every two inches.

Drilling mounting holes through the aluminum and into the wood base

I placed a strip of wood behind the back edge as a stop for the 1/4″ plate glass. I decided against fancy hinges and will likely add a strip of Duct Tape as a makeshift hinge.

I decided to add support for the Neoprene which was surprisingly heavy at a span of 40″. The black material was a leftover from the original frame. At this stage I realized I may need future access to the inside of the frame. I did not want to have to remove the Neoprene and weatherstripping, so the metal angle brackets were moved to the outside of the frame.

Simple support structure using 1″ x 3″ pine. Also seen is one of the aluminum mounting strips.

Here is the sheet of Neoprene (rubber) I purchased from Foamorder.com. It is 3mm thick, and is textured on one side with a nylon mesh on the other side. The textured side will be face up against the glass to allow channels for the air to escape. The pre-cut sizes are large enough for a replacement sheet for use in the future.

After mounting the Neoprene using the aluminum strips to hold it in place, I attached flat, closed-cell foam weatherstripping 3/4″ wide by 1/4″ thick. Unfortunately, this did not allow a vacuum to develop. I then added a small D-tube rubber weatherstripping on top which worked nicely. At the two seams of the D-tube material, I sealed the ends using a fast-setting rubber glue.

Two layers of weatherstripping to create a vacuum seal

Before mounting, I cut a 1/4″ hole in the Neoprene for attaching the vacuum hose.

The hose is attached to the sheet via a automotive tire valve stem. A small piece of leftover Neoprene acts as a guard to protect the glass from the chrome valve stem. The texture of the rubber sheet is very apparent here.

Chrome valve stem protected from contacting the glass using a small piece of Neoprene

For the needed volume I purchased a vacuum pump rated at 2.5 cfm. I mounted a power strip for easier on/off switch access.

I used the same gauge as my old setup. Here it is pulling over 17 inches of vacuum with the new frame. I have a bleeder valve (not shown here) for fine adjustment of the vacuum.

The image below show the layers. 1. wood base frame 2. Neoprene 3. aluminum strip 4. Foam insulation 5. D-Tube insulation 6. Glass

Finally, here is the new UV meter from Ian Leake (tapered box) which just arrived this week. Behind it is a controllable outlet box which will turn off the bulbs when the correct exposure has been reached.

And the remote sensor placed onto the glass. It is out of the way of the largest print I plan on making at 20″ x 25″ with the paper temporarily bonded to 25″ x 30″ aluminum sheets for accurate multi-layer registration.

As of this writing, the vacuum frame has not been used in making a print, having been completed only this afternoon. But, I did place a sandwich of paper mounted to metal, a negative and a carrier sheet into the frame and fired it up, and there appeared to be solid contact.

Links:

UV Meter: https://ianleake.com/light-counter-system/

Neoprene: https://www.foamorder.com/neoprene/neoprene.html

Low iron glass: http://www.starphireglass.com/

I Finally completed my new UV lights and vacuum frame. It will accommodate a full sheet of watercolor paper with room to spare. It uses 24: F30T8 BL bulbs and six electronic ballasts for the light source. The black skirt is made of felt and blocks stray UV. The bulbs are suspended just 2″ above the vacuum table.

Here’s a peek at the 24 black light bulbs. The end sockets are mounted to a sheet of 3/4″ maple plywood with a layer of galvanized steel in-between as a ground plane for the bulbs. Below the bulbs you can see three computer fans used to cool the bulbs during use.

An electric hour meter will keep track of bulb usage.

And here’s the vacuum table showing the Kreene film partially unrolled. The usable (black) surface measures 27″ x 38″ with an overall size of 35″ x 44″ of maple plywood. The vacuum pump runs on 12 volts and was re-purposed from an old automobile windshield repair kit. It is powered by a 33Ah battery and a smart trickle charger. At the front of the table is a bleeder valve to control the amount of vacuum for various processes. So far I have seen the pump pull a maximum 16 inches of vacuum on this table. The black textured surface was purchased from Lowes hardware and is contact glued to the plywood. Surrounding that is 3/4″ Velcro (self-adhesive, hook side). A hole is drilled near the upper right and lower left corners of the Velcro and brass hose couplers are epoxied into the holes on the bottom of the table. Plastic tubing of 1/4″ i.d. is fitted onto the brass pieces and connected to a “tee.” Then a single tube runs to the vacuum pump.