Help building vacuum frame (need pump suggestions)

[menglert]

I'm going to build a contact printing frame because I can't find one at a resonable price. I found instructions on B&S , but can't find information on what type of pump I need. I'm only working with 8x10 at the moment, but in the future would like to work up to larger prints of 20x24. So I will build the frame to accomidate that.

What type of pump should I get? What should I look for in the pump as far as features? There seem to be a lot of different options, and I have no idea how much power I need.

Any other suggestions from those who have built a vacuum frame in the past or have expeniece with them is welcomed.

Thanks,
Martin

[Donald Miller]

I'm going to build a contact printing frame because I can't find one at a resonable price. I found instructions on B&S , but can't find information on what type of pump I need. I'm only working with 8x10 at the moment, but in the future would like to work up to larger prints of 20x24. So I will build the frame to accomidate that.

What type of pump should I get? What should I look for in the pump as far as features? There seem to be a lot of different options, and I have no idea how much power I need.

Any other suggestions from those who have built a vacuum frame in the past or have expeniece with them is welcomed.

Thanks,
Martin

Martin,

I am assuming here that you are speaking of a vacuum easel that has perforations through which air is evacuated to hold the paper flat. If I am mistaken, then what I am about to relate will probably not apply.

Once the openings in the easel are obstructed by the paper then you will not need a vacuum pump to pull a deep vacuum. An example of a deep vacuum pump would be a two stage pump that evacuates refrigeration systems.

The higher the CFM vacuum pump that you can obtain will serve to hold the paper down quicker. The thing that makes the most sense...the most bang for the buck, so to speak, would be a used tank vacuum cleaner...if you provide a large enough opening into the easel to accept the vacuum cleaner hose you can probably get this done for very little money. Pawn shops usually have a ton of these things laying around for less then $20 bucks.

The downside is that they are fairly noisy...but you could remotely position it.

[BradS]

shop vac.

[Allen Friday]

I use a shop vac with my frame.

[menglert]

Thanks for all the quick advice.

So as I understand, I don't need a powerful vacuum, because the power will only determine how fast the contact is made, right?

Shop vacs seem to be a good idea. Do you use anything to make the hose opening more narrow?

-Martin

[edz]

Shop vacs seem to be a good idea.

No. They are not. Vacuum cleaners are a cheap but not good idea. They are designed and intended to suck but not to suck hard (closed intake) for longer than a few seconds. They will get very hot. They are also not terribly constant so no only unreliable (if one is sitting on a bunch of old vacuums perhaps not that much of an issue) but inferior. In a frame you want a reasonable (relatively low underpressure but with moderate volume capacity) a vacuum and you want to hold it, typically, for longer than just a few seconds. If you hunt around, however, and with a bit of luck one can find a surplus rotary vane industrial pump (costing new many 100s of USD) for less than the price of 10g, maybe as much as 25g, of silver nitrate.

[Joe Lipka]

Gast makes the vacuum pump used in the NuArc vacuum frames. They are almost bullet and fool proof. Google Gast and see what they have. You should be able to purchase through a local industrial distributor.

Don't forget you need a vacuum gauge to measure how much your apparatus sucks. No, seriously, sucking for a vacuum frame is a good thing. Vacuum gauge is important because you need to maintain a specific vacuurm level as part of your printing routine. The level of vacuum, or how tight the negative is pressed against the paper is key in maintaining consistent highlight exposures.

At least that's been my observation. Your mileage may vary.

[TimVermont]

I have a very small Gast pump. Noise and vibration are issues you'll need to solve. I used rubber washers, nylon sleeves around the mounting bolts, cork and felt. Use only a small section of soft flexible tube to avoid loss of suction. I use hard fiber reinforced tubing for the long run.

[Richard Wasserman]

I bought a small vacuum pump and gauge from McMaster Carr. It's a bit slower than a larger pump, but a lot quieter. I also installed it outside the darkroom on a styrofoam pad.

Richard Wasserman

[menglert]

Thanks for all your advice so far...

I'm looking through some different pages, and at the Gast pumps. There are a lot to choose from with different specs. What is the minimum vacuum "psi" rating I should use for contact printing? Are there any other specs I should be concerned with while choosing one?

-Martin