Invisible graffiti
Working on a building site you see the usual dull racist homophobic graffiti, but it was the plasterers that were subtle.
As they would graffiti on the plaster board wall a few their names for prosperity, but others would draw tits or 'you cunts/wankers etc' knowing that whoever worked or lived in the building would be there and not realise what is actually surrounding them, which was mildly amusing for a short time.

Decorators would also leave their mark, I was refurbishing my first house about 20 years ago, it hadn't been redecorated since the 50’s or 60’s judging by the top layer of orange flowery wall paper, so it all had to be removed.
I was stripping back the multiple layers of wall paper, having to do it very carefully as it was on the original lath and plaster walls, I stripped it back on the main wall and gradually revealed written in pencil in large letters, 'you bloddy queer' (sic) tastefully illustrated with a picture of a large hairy cock and balls. It made me laugh that some 50 years after it was done it did its job.

Nice to know some traditions in building are consistent
(nimrodihnio making gravy for one., Wed 13 Oct 2010, 19:35, 3 replies)

Reminds me of this that appeared in a trade journal recently
www.thisisgrimsby.co.uk/news/Family-set-challenge-rest-electrician-s-hidden-notes-past/article-2662047-detail/article.html
( bane, Wed 13 Oct 2010, 21:20, closed)

nice
I love pineapple crush, good job he didn't draw a big cock on it or it would have spoiled everything.
I also found old handwritten receipts and bits of newspapers from the 1950's under the kitchen lino.
(nimrodihnio making gravy for one., Wed 13 Oct 2010, 21:56, closed)

One of the dining room cupboard doors in my house has writing from the early 1900's on it. Must take a pic and post.
( dazbrilliantwhites has been meaning to change this..., Wed 13 Oct 2010, 23:16, closed)