on our recent holiday to cyprus my wife and i had our portrait done in charcoal, measuring for frame size we inadvertently got grease on the back of the paper and it has soaked through to the front of our portrait in 2 or 3 areas 1-2 cm in diameter. how can we remove these marks without ruining it further please ?
The warm iron method does reasonably well and won't do any more harm, but if you can get some real blotting paper (remember when people wrote with those funny wet ink pen things?) it is much more effective. (seriously, a good stationers should keep it)