Another Method of Float Mounting

[framemaker]

A few weeks ago I was trying to work out how I could float mount copper sheet, and other heavy items. This is one method I have now tried, (a basic outline was suggested by Prospero) I am sure there are others who have done this before for use in framing, but the method has been adapted from reading articles on mounting various objects, such as tiles by the V&A, and in the making structural repairs to sculpture.

The copper sheet (200mm x 200mm x 1.2mm) had to be float mounted on mountboard, with a floating effect of about 5 to 10mm. I cut the backing mountboard (375 Colourmount), and the 6mm MDF back. I cut four blocks of obeche fillet, 9mm x 40mm x 40mm. The outline of the copper sheet was drawn in pencil on the MDF, and roughly where the wooden blocks would be positioned. I drilled a hole through each block and the MDF for the fixing screw. The rough position of where the epoxy adhesive would be was also marked (about 15mm diameter) all around this area very small holes were drilled, these 'vent' holes would make it easier to reverse the adhesive bond in the future. This can be done by fuming or by careful direct application of the reversing solvent into the holes.

I then weighed out 20g of Paraloid B72 acrylic resin pellets, these were put in a glass bottle with ml measurements marked on the side, then acetone was added until the level reached the 100ml mark. This gives a 20% W/V mixture. This was left overnight to dissolve, and after shaking and mixing well an even coating was applied to the back (which I first sanded lightly to give extra 'tooth') of the copper sheet, where the four glue points would be, and also to the four wooden blocks. This was left for 24 hours so the acetone could fully evaporate before a second coat was applied, and then left for 48 hours.

The copper sheet was then ready to be fixed to the four wooden blocks. For this I used Araldite 2015 epoxy adhesive, which is a toughened high strength adhesive paste. A blob of epoxy was applied on the four wooden blocks and a weight was placed on the copper sheet while the adhesive cured. In practice I think I used a little to much epoxy, I was aiming for a 15mm x 0.5mm layer between the wood and copper, but it spread a bit further out than this.

To remove the piece in the future, the four screws would be undone, leaving the four wooden blocks fixed to the back of the copper, these and the epoxy fixing them could be removed by reversing the Paraloid barrier layer with acetone, toluene, or xylene.

The benefit of this method is that there are no visible fixings, the long term strength of Araldite is well known, as is the stability and conservation suitability of Paraloid. I think this method would be suitable for framing various objects such as tiles, plaques, where a stable, long term, but reversible bond is required. I think it would be particularly suitable for mounting tiles and other stone type objects. I know this method will not appeal to everyone, but I think it could have its uses.

In a few weeks I plan to take the frame apart, and attempt to remove the four wooden support blocks from the copper. Theoretically it should be possible to totally remove and reverse the adhesive barrier layer, so I will post how I get on doing this!

[WelshFramer]

Great. Look forward to the progress report.

Where do you get the Paraloid B72 (apart from Robo who, I'm sure, must sell it in his craft shop)?

[framemaker]

Hi Mike

you can get it from Preservation Equipment, Conservation by Design, or some arts suppliers like Cornelissen.

You can buy in pellet form and mix yourself, or I think you can get a ready mixed 20% in acetone. It can also be bought in tube form (a 50% mix I think, made by HMG and similar consistency to UHU), I have used this for repairs to tiles and ceramics.

The solvent you mix it with and strength will vary on the application, for example I usually use 5% to 7% in toluene or acetone for consolidating gesso/gilding on antique frames.

It can be used as a varnish, and in numerous other tasks. It can also be bought in a spray can as Lascaux Fixativ, which I think is probably one of the best fixative sprays you can get.

[Roboframer]

Formed rods would be visible as would things like Mighty Mounts, Melinex would be visible, it would at least make it shinier than it started out, plus something like this could just be too large/heavy for that anyway.

These methods and others that hold rather than stick have their price - you can see them - even if it means you have to look really hard.

Glass that offers the highest UV protection also has it's price - colour shift and a visible ripple with TruVu conservation clear/museum glass, price and weight for laminated products which don't have that ripple and far less coluor shift - blah blah.

If you strive to always find a way to mount things in a totally reversible way - IOW there's nothing to be unstuck, just undone/unfastened, then what do you do if the customer (client if you're posh) insists on something like this floated with absolutely nothing over the front?

Well, probably just stick it down, which is fine, maybe, when the customer's choice is an informed one - I mean what else do you do, refuse the job?

Some things, like tiles, which are intended to go on walls ...... but you must frame instead ..... you have to take in to consideration how, if they were on a wall, would they be fixed to it. Well, they'd be stuck to it , and removal would probably involve a chisel!

There's 'no-brainer' methods which would achieve the same visual result, like Evo Stick contact adhesive or 'no nails' but it's good to know of a 'damage limitation' method like this.

Thanks for your time/sharing.

[framemaker]

I took this frame apart yesterday to see how easy it was to remove the Araldite holding the copper sheet to the wooden blocks. It went very well, I thought I would first see how easy it was to remove the blocks by force, I used a screwdriver to prise off the block, this took a reasonable amount of effort. I expected the bond to fail between the epoxy and the copper, but in fact it was the obeche wood that gave way first, which says something for the all round bond strength of the Paraloid and epoxy.

Next I used toluene (wore a respirator while using this) on the second block, this was flooded on the back of the block and the holes covered in tape, so the solvent could work from the inside. Over the next 30 minutes I reapplied the solvent a number of times in the holes and around the block. After 45 minutes the block came away very easily, leaving just the epoxy adhered to the metal, another brushing of solvent and the epoxy easily peeled away from the copper. With all the blocks removed the last traces of Paraloid were removed solvent and a rag.

It was alot of messing about, but still a useful experiment. To be honest with mounting metal you probably could just forget the Paraloid and go straight in with the Araldite, if it need to be removed you could carefully prise the blocks off and just grind off any wood/epoxy residue with a Dremel.

I have now framed a piece on aluminium for the artist who originally wanted sheet metal floating. It came out very well, although I used a 6mm x 47mm subframe instead of the 4 blocks.
I am now doing one on sheet steel (heavy!), this subframe will also have cross bars to provide extra strength and surface area to bond the metal.