Hello,
I saw many nice projects in this forum, so I suppose someone here is able to help me with my problem. First, I will explain my plan: I am trying to build my city in a little diorama. And, for this, I want to build my own house. And my house has, like many, a chimney. Building the chimney is not the problem. But I am wondering if it is possible to let the chimney smoke. If you had an advice for me, I would be very greatful
Greetings, Melly

Model railway engines used to smoke. I believe that some kind of heated oil was involved. Maybe trying something similar would help.

Hello Melanie ! Maybe try something like this:
http://www.faller.de/App/WebObjects/XSeMIPS.woa/cms/page/pid.14.17.89/agid.1128.1196.1127.1202.1229/atid.1088/lg.en/ecm.at/index.html

This is smoke generator uses in train dioramas.

You might be disappointed with a locomotive smoke generator - the ones I've seen only make small intermittant puffs of smoke. If you don't want to go that way, you could use a piece of absorbent cotton (or a cotton ball) stretched out.

I agree with Biggles here. In this case,with the cotton,less is better.
J

First thing to consider is, what is the fire burning? If it's wood there will be much less visible smoke than if it's coal. Peat is different again. Which fuel it is will depend where it's located and how good the local rail connections are. And even if it's coal, the smoke won't be black - it will be mid-grey and, unless there's a fault with the chimney, it won't come out in a dense cloud either.

+1 with Biggles and Jer, white cotton pulled into a slight wisp.

Less is better with this effect - just a hint of the smoke. Too much looks just like a stretched out cotton ball, too little disappears. However, between the two, too little is much better and more realistic than too much.

People see what they expect to see and their imagination easily fills in the rest. A cotton wisp coming from a chimney fools the viewer's eye into seeing smoke.