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I hear everyone say on the forums that they hate sanding because it takes so much time, but I find that sanding spackle takes hardly any time at all. Does gesso take longer to sand than spackle, or am I just a freak that seems to like sanding and doesn't notice the time go by as much as everyone else. *laughs*
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I'm confused. Isn't Gesso a thickener for artist paints?
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Hi Seeria,
gesso is a mixture of ground chalk, and animal based glue (mainly). It dries to a very hard stone like finish and can be worked to produce a very smooth surface. Think early European paintings using tempura and oil on board. Vermeer was one of the best examples of the quality of surface that can be produced.
The trick on a flat surface is to paint a thin layer that is allowed to dry, this is then scraped over with a specific tool (a bit like an old fashioned wood two handled wood plane). Another layer is then painted and so on. The process is long and back in the renaissance the artist would probably spend as much time preparing the board as laying down the first underpainting. It is also why boards were often reused.
Enough of the history :oops:
For Papiermache gesso can be the same fundamental mixture and can be applied in the same way. We have to sand each layer with paper or wire wool, rather than scrape, because of the 3d nature of our work.
There are other options for similar finish but fundamentally gesso is probably the best.
Hope that helps,
Charlotte.
(The pedant, artist workshop practice was my major at Uni)
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newmodeller: You sound so amazingly knowledgeable on this topic. I hope you don't mind me asking you a question. I have been confused for so long on what the difference between gesso and spackle is. To the best of my knowledge they are both made out of a whitener and glue. I've been using spackle because gesso is *so* expensive - but if gesso is fundamentally better I'd of course want to switch over but I don't know which one is better because they seem to contain the same ingredients.
I hope I didn't lose you, I kind of talked in circles there. *laughs*
In your opinion, is one better than the other?
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I don't know a lot about it, but my research has indicated that gesso is calcium carbonate mixed with glue; spackle (generic term, spackling compound) is gypsum (calcium sulfate) mixed with glue. Both of the calciums are limestone-based, but I don't know the differences in how they behave, OR if they're interchangeable.
I believe that gesso is mainly used as a painting ground, and spackle is used to fill cracks. Several kinds I've used for home repair indicate that if the material is applied too thickly, it will crack. I've also read that if gesso is applied to flexible materials like artist canvas, it will crack.
But, I have this compulsion to use things (tools and materials) NOT as they were designed or intended. Sometimes they work, sometimes they don't.
When I have bought acrylic gesso, I was disappointed in its wateryness (is that a word?). I want to use it on PM to fill holes and dents, to smooth out the surface, and I want a thicker material. Since chalk is a relatively soft material (possibly easy to sand?), I was wondering if mixing it with regular acrylic paint to the thickness I want, would provide the surface smoothness that I seek.
I know the spackle cracks if applied too thickly 
. Now I just have to get to work and see how the chalk acts with acrylic paint, and then latex paint.
Sue
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CatPerson: I have been using spackle and I love it. I haven't had any trouble with cracking yet at all. I put it on in thin layers and rub it in so that it fills up the cracks and dents.
I am still a baby beginner in papier-mache though, so for all I know it could crack in the future. I'll keep an eye on things and let you know how it goes. I highly recommend playing with spackle! I love the way it feels, and I love how the way it sands when you get two or three layers on it.
I did put some chalk in my glue today as well as per your always wonderful advice. I'll update you on that goes too! 
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Thanks for the clarification, got me thinking of new tests to run after the move.
Butterbee, are you adding anything to your spackle? I've tried a few tiles with straight spackle (and even joint compound) and found they do crack, especially if put on flexible surface (paper sheets dried). Would love to find a way to use it without it cracking.
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Seeria: Nope, I don't add anything to the spackle. I just buy it pre-mixed in small buckets. I know the powder is cheaper but I don't trust myself to mix it correctly.
I am not sure why it isn't cracking when I use it. I put bunch of thin layers on and sand. I am totally curiously about this mystery now. When did it crack on you? I am just beginning at papier-mache so it is possible that the spackle will crack later on and I just don't know about it yet.
Are you using Gesso instead Seeria? I am wondering if I should move over to gesso because everyone seems to like it so much. It is just so expensive though. I am not really sure I can afford it. 
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Never touched Gesso, unless you count looking at the price tag at the craft store and fainting. heh
Two reasons my spackling probably cracked: 1. flexible material I put it on (paper sheets, somewhat bendable not rock solid); and 2. Probably too thick. I'm not using it recently, unless you count making nifty designs on the walls then painting over them. 
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What I've read is that if your gesso is too thick with chalk, it cracks. So does cpackling.
Gesso is used for smoothing the surface of canvas before painting. You should (if you're gonna put on two coats), put down a thin coat first, then a liberal coat. Also, work in one direction for the first coat (vertically), then the other (horizontally) for the second. Then allow to dry for a full 24 hours before painting on it.
Wikipedia says Gesso will crack if there's too much chalk in it.
With this knowlege, I tried making a pulp that is made from paper + chalk. The result was better than just paper alone, but it still ends up lumpy. Also, this dries terribly hard and is difficult to sand.
The best thing I've found for smoothing easily is paper clay. If you put down a thick paper on your piece, this causes a lip. Round that lip by filling it with the paper clay. This paper clay is very soft and sands away very easily (too easily, so be careful). Once sanded, cover it with glue to harden the clay. Then Gesso it, and sand with a medium paper grit (220).
I was quite ANNOYED to see that this clay costs over $5 US for just 8 ounces, but it turns out that a little of this goes a long way. Use it sparingly, and only to do smoothing or where first applying pulp, then paper will take too much of your time.
I'm gonna try what's called corner compound. This is the stuff that plasterboard joints are filled with. This may be easier to work than spackle (which I would NOT attempt using due to it's hardness). I'll let you know what I find out.
There seems to be a trade off. You either gotta spend money or a lot of time. Sheesh! Either way it costs you a lot of time, so I'm gonna spend money to speed things up. Besides, the result is better this way too.
Now.... can somebody tell me why styrofoam is so freaking expensive? a 12" x 12" x 12" cube costs nearly $15!! That's just plain ridiculous!
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I'm gonna try what's called corner compound. This is the stuff that plasterboard joints are filled with. This may be easier to work than spackle (which I would NOT attempt using due to it's hardness). I'll let you know what I find out.
Lengo, I am confused to why you wouldn't try using spackle. I am currently using it and so far I love it. What really confuses me is the statement: 'I would not attempt using due to it's hardness.' To me, this is the best part of spackle. It's smooth finish, ability to sand, and its hardness.
Is my direction of thinking wrong? Please let me know what I am missing. I am so new to the medium that I am terrified everything I do is a mistake.
If it wasn't for catperson patiently telling me over in over that nothing I can do is 'wrong' I'd probably get nothing done at all!
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B bee
Catperson is right you will never know until you try. People work with different materials. I like using PVA while others hate the stuff but it works for the type of work I'm doing at the moment.The great thing about mistakes is you learn by them and try again. The idea is to relax enjoy yourself have fun Who cares if you make mistakes it will make a interesting talking point,
If you like using something and it works for you carry on.
Sue.
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ButterBee,
I am with Sue on this one, nothing you do with art is ever a mistake. It may not yield the result you are looking for but sometimes that 'mistake' may just push you off in a direction you never expected.
One word of advice, keep notes of what you do. there is nothing more annoying that getting to the finish of a project and realising that you have forgotten what you did on the way.
Plunge right in and have fun, methods and recipes are fantastic but are only the start.
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Lengo: Did you ever end up trying corner compound? I was just wondering what the results of your experiment were.
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