Hi. I'm using Yeso to build in some light blocks at the top of an interior wall. Also intending to have a go at using Yeso to plaster the walls. Can anyone here tell me how much ammonium to add to my yeso mix to delay it's setting time. And how long that delay is for?
Also what's the best Yeso water mix?

Are you aware of the two types of yeso? One is for plastering (yeso liso I think) and the other is for 'fixing' the latter does indeed go off very fast.

It's all really, simply practice. A lot of brit 'builders' that I know can't use yeso for plastering but having persevered, it is actually just the same and in some cases can give a better finish.

None of the Spanish builders that I know use any form of retardant - simply put water into the bucket and add the yeso until you've made a sloppy custard. It then starts to get thicker the longer you leave it. They tend to scoop through the top (watery) layer with their hands and then trowel from there!

Best of luck.

I'm pretty sure we once within the past couple of years bought something actually called Yeso Retardo or Lento or something?

For plastering the walls you could try using products called Perlita or Escayola - I find them much easier than Yeso which simply goes off too quickly.

Thanks for that. I actually accidentally bought the really fast one first time so I'm using this for fixing the light blocks and building built in shelves with bricks and rasillones. Really cheap! I'll look for the liso when I'm done. I reckon when I've got some experience with the really fast one the other will be ...if not a doddle, much more manageable.
By the time I'm finished my brand new build will look rustic... more by accident than design. But no bad thing because its a complete rebuild of an old house in a terrace. So it will look more in keeping!
BTW anyone want to come over and help with plastering in return for a website...or any other skill we can swap??

No way Jose - my plastering's not my strong point
BUT
you've hit on a brilliant idea, if only enough of us were close enough to each other; the LETS scheme is one I champion yet geography seems to get in the way in this large country!

ps yes I'd love a website, just not in return for plastering

there is actually 3 types of yeso. "rapido", which starts to go off almost instantly, "controlado", which is not just quite a quick, and a "finish", "yeso fino de acabad", which is quite slow

Controlado is like a base coat, (such as carlite browning) and the "finish" sets slow enoughto allow a"polished" top coat.

Well LETS see if there are other ways to help each other. PM me things you can do which might help us! Given that you know a few things about our life:-) Or I'll contact you. Whoever gets to it first.

Right.
Another idea is maybe there's someone out there prepared to teach me plastering with Yeso. I do know it's not so common these days. Only the oldies do it here and they're all too old and toothless to teach me (too campurriano in their speech and too weak in their bodies!)
BTW after a day attaching light bricks I feel too old and weak too!

capa fina

Please do NOT mix capa fina and yeso. capa fina, as I understand it, is like finishing plaster.

Snikpoh has the answer, it has to be mixed by hand in small amounts in clean buckets and used very quickly.

Was it DIY SOS plasterers that mixed a whole bucket up and it had gone off by the time it got to the scaffold ?

So is Capa fina like plaster of paris? Is it a type of Yeso>
The light blocks went up very quickly...well they had to!!
Fortunately I have some little rubber bowls which were perfect for the job. One little bowlful made up fresh for each block. Tried retarding with Amonia but it made very little, if any, difference and stunk to high heaven. Brilliant cleaner ammonia though! I remember that smell from bucketfuls of babies nappies in the back yard. I used to soak them for two days just in their own urine diluted with not too much water. Take the lid off and the ammonia smell really hit you!
Then I rinsed them thoroughly and washed them. Only the dirty ones went into nappy cleanse. My kids nappies were the whitest on the street! OOh I do sound old! Can't remember who taught me that trick.
There you are bil. When you've stopped weeing on the compost you can get the whites right!

I am NOT.
There is an exterior and interior. Interior gives a smoother finish both come in impermeable.
It is the most popular here as it is workable for over an hour, does not need to be painted and when it is, paint adheres to it better.
I have heard that some people use washing up liquid or lemon juice to retard yeso but I have always followed the local builders and used capa fina to plaster and I am more than happy.

I absolutely agree. Capa fina is an alternative to using yeso and can come pre-coloured.

... but that wasn't the question that was asked ...