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How to cast pulp.

Hi I want to make a daruma doll. Like in the video. How do you cast pulp into a hollow item? like in the video? Its pretty cool how they make them. ANybody do anything like this? I don't want to papermache with newspaper I want to make it like in the video.

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Kiteman5 years ago

That's clever.

As far as I can see, they are vacuum moulded - the box they lower into the pulp has holes top and bottom, pulp flows into it into a cavity lined with mesh in the shape of the model.

A burst of vacuum* from the hoses sucks the water through the mesh, leaves a thick layer of pulp on the mesh.

Lift it out of the pulp, give another burst of vacuum, and you'll have quite a rigid structure.

Drying can take hours to days, depending on temperature, air-circulation and humidity.

The hard part reproducing this will be making the mould - you'll need a stiff metal mesh.

What will *not* work well is pressing the pulp into a waterproof mould, because pulp doesn't set, like plaster or cement, and it doesn't cool and solidify like molten metal. It has to dry through, and if you cover it in something waterproof, the water isn't going to be able to evaporate.

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If you aren't able to use mesh and vacuum, you'll have to "cast" around a solid object, like traditional papier mache around a balloon. Make your pulp, paint or press a thin layer onto the object, and let it dry. Add a few extra layers, letting it dry each time.

When it is properly dry, cut around the "equator" of the mould and lift off the papier mache form.

The finished models are shiny because they have used a very viscous paint that has filled in the rough texture of the paper-pulp. If your model is strong enough, you may be able to sand it smoother before painting it.


* Yes, I know
undftdking (author)  Kiteman5 years ago
WOW I never thought of Vacuum, I was wondering what the hose ontop was for thanks so much it really helped. I'm a little sketchy on the mesh though I wanna see what others' Ideas are.
sazure1 month ago

Kiteman, thank you for your reply. I have many books but all are packed away. I knew if vacuum molded plastics and recently looked up paper molding (industrial) and came across Paper Pulp Molds (industrial for example egg crates for eggs) and this article on someone who made their own

http://www.papermodelers.com/forum/tips-techniques...

(as a fellow student - engineer type, back in collage did to mold plastic - needed heat and suction to pull air out, a process that is for sure).

..................

Aeray - after ages of searching your reply gives me "hope".

I came here for another quest - I want to make smooth paper mache hollow spheres not a build up, and again decades of books are stored (lived in NYC for 33 years as well so classes, mostly in advanced ceramics and mold making/slip casting so on BUT a most amazing library with old formulas or hints when the author did not state the ingredients).

Like a half form (where two could be joined, shapes cut out so forth) and was wondering about a plaster negative mold, with some sort of "gel" coat (release) and then I would use (who knows until I experiment) plaster strips and then paper strips but not paper mache (too thick for what I want).

I am now in a City where the library has few books on the arts.

I want a super smooth form (outer form) and know from experience a build up will not be as smooth as I want (glassy smooth!).

Have you used the plaster form for such (as well would not be able to use any sort of plaster or plaster strips) but some material that would resist the plaster mold and still create an initial glassy outer first layer - can build up after that.

Was trying to experiment on a very small scale but maybe should wait until I can dig my books out! Thanks for the world wide web and your replies!

sazure sazure1 month ago

Lol I just saw how old this thread is!!! Well it all adds up!

aeray5 years ago
I think your best bet would be to use a plaster mold, like those used for slipcasting ceramics (try that as a search term). Pulp can be made fairly easily at home using a blender. The liquid pulp would be poured into the plaster mold and left to sit for a while (you'll have to experiment a bit). The plaster will pull water from the pulp, forming a dryer "skin" on the inside of the mold. The extra liquid pulp can then be poured out. As the "skin" dries, it will pull away from the mold and release. Mix the pulp as thick as you can and consider using a bit of sodium silicate (waterglass) or, in the US, Darvan 7, as a deflocculant, to decrease the amount of water necessary to make the mixture "flow".
elifat aeray4 years ago
Good morning

its amazing the way that make a figure like the video using this kind of mold.

someone knows how this mold works? its based on vaccum pump?
some have a drawings in order to show how is the mold made?

im interesting because i like to built figures by paper mold.
I apreciated someone tell me how is this mold charge the paper pulp in the mold and how its the paper sticking in the mold and allow the figure is taken off finished.

Regards Eli Olveda.
Hi aeray,

Is that so simple? No other material needed? Does it work with bigger objects as well? Waterglass is a powder or liquid?
Thanks
Waterglass (sodium silicate) is usually sold as thick liquid. It should work on any scale, as long as the thickness/mass of the plaster mold was sufficient to pull away an adequate amount of water. The thicker the mold, the more it can absorb, but the longer it has to dry between castings.
Aeray, thanks for your answer.