aahhh yes - those lovely mass produced oil paintings that often get sold door to door by people posing as struggling art students trying to make their way through college by selling their work - or sold in mediteranean villages by "local artists" - all good fun & profitable too - if a "little" dishonest at times.....
OK so how do we tackle them???
Well the first thing to ask is - "why stick them down"??? - the answer usually being that because they have been "creased by the weight of my flip flops & cheap vodka in my holiday suitcase and look a mess". They seldom have any spare canvas for stretching - so mounting is an obvious solution.
The next comment & question is - "they are an original piece - will I impair their value by glueing them to a board"??? - the answer is "what value"??? They have no commercial value as an original & will certainly not appreciate in value in the future - so the choice is - "do you want them to look good" or "do you want to maintain their value of around £5 & look rubbish.
Assuming we want them to look good I have two ways that I handle this type of work - the first is pretty radical - but it works a treat!!! Cut a piece of MDF (3mm) which you will also use for the back of the frame (cheapskate) - or if you prefer - cut a piece of good quality "impact board" - such as white display board or similar. Do not use foamboard / mountboard / corrigated board / grey board / pulp board - as these are all too soft & will soak up the adhesive we are about to use...
Next take a tin of carpet tile adhesive spray (B&Q do a great one) - ventilate your room & spray your backing board librally. After you have recovered from the fume induced high - take your painting & pat it down carefully on to the tacky board in the desired position & then cover the entire board with a piece of silicone film or paper. You will be throwing this film or paper away at the end - so maybe use an old piece.
Now place the work into your press & cover the assembly with several sheets of foam & apply pressure - BUT NO HEAT for about ten minutes - result a painting "welded" to board. The reason for the foam by the way is to stop the platen of your machine from crushing raised areas of paint.
The second method is slightly "more professional" but will require investment in a roll of Dry Mount Film (don't worry it has lots of other uses too - once it is under the work bench).
Firstly set your press for 90 degrees C or 195 degrees F & let it warm up. As it is warming cut yourself a piece of MDF or White Display Board again & cut a piece of Dry Mount Film to the size of the painting or 10mm larger if you have left a board of board. Normally Drymount Film needs piercing - to allow air movement - but this combination of art & board breathe OK - so you can skip that step.
Now peel back one backing paper of the film & press it onto your board - it is "self tacking" so it will stay where it is put. Now place your board & adhesive in the press & press it for about 4 mintues - remember the second liner paper should still be affixed to the film - to protect it at this stage.
When your film has bonded to the board & whilst the board is still hot - peel back an edge of the second release paper & attach the edge of your oil - gently pulling the rest of the liner away as you smooth the artwork down. This latent heat will allow the picture to "tack" but not stick to the board.
Finally repeat as before cover the assembly with silicone film or paper & then cover this with some sheets of foam & cook at the same temp (90) for around 5 to 6 minutes. Result - a painting beautifully stuck down - with a barrier layer of plastic within the mount film to stop acids attacking your "masterpiece" from behind long into the future...
Incidently - I have two lovely greek fishing village scenes in my bathroom - lovely to look at whilst soaking the strains of the day away with a glass of Retsina
Although vacs need a bigger 'footprint', they are lighter and can be built into a bench. I made a table to fit mine where the top lifts up when you want to use the press.
- all presses have a flat bed & the term is applied to printing presses - not mounting presses - OK stress over... 
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