How to modify a film holder for wet plate collodion: design #2: magical magnetic tape

Elizabeth Graves develops another impermanent, non-damaging way to hold thin metal plates in a conventional large format film holder.

Writer and photography / Elizabeth Graves


Image of a large format film holder modified to hold metal plates
The plate holder, showing the medium gray magnetic tape around the edges of the (red) plate, plus washers clinging to the magnets and holding the plate by its corners.
I went overboard with the magnets here while trying other sizes of plate, but it is only needed in the corners.

One day, you’ll be milling about near your large format camera and will be struck by a vision: a vision of a perfect composition for your wet plate collodion work. The catch: the composition requires a different size of plate than you are currently set up to use.

Perhaps that Dream Plate is square, which is a proportion there are no common film holders for. Perhaps you are working at “full plate” size (6.5″ x 8.5″), but for this subject, you want to make a plate that is just 4″ x 5″. You may only want to make one image, or a few images, at this other size. But you know that having a plate holder made for you can be prohibitively expensive, and you don’t want to destroy your existing film holders on a lark, so you think you need to give up on this dream.

Think again! Thin, soft, adhesive magnets can solve your problems.

You’ve seen these types of magnets. They often come in the mail with the logos of charities on them, are used as business cards for household services, or are coupons shaped like pizza slices that are used to reward you for loyalty to your local pizza parlor.  (Collect 10 magnets and get one free pizza! Mmmmm. Pizza.) This thin, flexible material is available in hobby shops in business card sizes and as rolls of adhesive tape with a paper backing in a wide range of sizes, so that you can stick a gentle magnet anywhere one is needed in your workshop or darkroom. Importantly, this magnetic tape is as thin as.63 mm (.025 inches), so it is thin enough to fit into the paper section of a film holder beneath the dark slide. This means it can be used as a “temporary” solution to modify a conventional film holder to handle your plates, without needing to make any permanent changes to the holder.

What you’ll need:

  • a complete large format film holder
  • magnetic adhesive tape
  • flat washers that stick to magnets (zinc-coated work)
  • some ordinary adhesive tape (optional)
  • the dimensions of the plate you want to use, along with the location on the holder that will be optimal for using that size. A plate cut to that size is ideal for testing the setup.

The illustration (shown here with a red plate) is largely self explanatory, but here are the steps:

1Measure out the center
of the film area of the film holder, and locate your plate where you believe it will be best. I center mine. (I make an x from corner to corner, and measure outward from the center of the x to outline my plate.)

2Put the sample plate
where you want it on your measurement markings. Hold it down temporarily with ordinary tape, if needed.

3Stick the magnetic material down
on the film area of the holder so that it surrounds and supports the plate at the plate’s corners. (I put it down in larger areas, but that wasn’t necessary.) Be sure to leave enough room to easily get the plate in and out of this little frame. The intention here is that the washers will stick to the magnets, and hold the plate in place when slid into a “photo corner” position. (The aluminum plates will not stick to the magnets – aluminum doesn’t do that!)

4Test the magnet-washer strength
by loading a plate into the holder, and trying to hold it in place with the washers overhanging the plate’s corners. Turn the holder sideways and even upside down to test how strong the hold is. For thin aluminum plates (.02 inches =.5 mm), the washers may be adequate. For heavier (.025 inch =.63 mm) plates, it is best to have the bottom of the plate held in place by washers that are taped into place with ordinary tape, since the bottom is where the plate is most likely to slip out of the holder. With a partially taped-down setup, you’ll slide your plate under the ‘fixed’ washers, and then slide the free washers into place to secure it.

5Check it!
Be sure the full assembly still fits under your dark slide!

Once your plate is sensitized in the darkroom, just drop the plate face up into the magnetic outline you’ve made, slide the washers into place over the plate’s corners (aside from the bottom washers you may have taped down), close your dark slide, and you are ready to expose!

If you decide not to continue with this size of plate, just peel the magnets off, and clean the remaining adhesive with the solvent of your choice. (Drugstores sell solvents specifically to remove adhesive “goo.”)

This design is an improvement over my first design, shown in Against all good advice: how to build a large format camera for wet collodion work at home, which required handling thin string to fasten the plates in, which proves difficult with wet gloves.

You don’t need to dream only in half-plate: you can work with plates any size you like within the dimensions of your existing film holders with this inexpensive, versatile technique.

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2 thoughts on “How to modify a film holder for wet plate collodion: design #2: magical magnetic tape”

  1. My understanding was that the darkslide will not cproperly close over a tin plate set up like this because the set up is too thick. The adaptations I have seen usually cut out the the centerplate and attach wire to the corners. Does yours close easily using tape and magnets

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