Bob do you have a laser or inkjet printer?
When Charly was here last week she did a pic for a sign on my shed "Beware of the Grump" using this method.
Can't show cos it all fell off when it dried out, something was wrong dunno what but maybe cos I have laser printer.
http://www.youtube.com/watch?v=BZ-fSm9LyOs
My printer is an inkjet Brian so will probably work but you haven't half brought back some distant memories
Along, long time ago I was involved with an American company called Binney & Smith who make Crayola crayons and Liquitex acrylic paint so I had quite a few samples and it just so happens that there are both matt and gloss gel among them. I know where they are though possibly dried out - hope not.
One of our tricks was similar to that video except never tried a printer, we used magazine pics and the results were pretty good.
As an aside, we had an industrial waste product which we called "sillyputty" and marketed it in a plastic egg. Amazing stuff, just like plastic putty, pink and could stretch it, bounce it and transfer print on to it. Never managed to sell in large volume as it was too expensive but the kids loved it
edit: Just googled and they still sell it. There are diy instructions on line as well
whilst a real spark plug might not be possible, it wouldn't be difficult for me to turn and carve a detailed spark plug in box or lime. Will think on that one.
