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Scout 09-04-2014 06:28 AM

Sculpting with cement
 
I am trying out cement instead of clay for a while. It's quite the challenge. There don't seem to be any forums for cement so I thought I'd come back here and see if I could get any interest going.

I have been consumed with watercolors for a while but now I need to sculpt again. I am doing life size people.

Does anyone have an interest, or better, any information?

Andrew Werby 09-04-2014 03:17 PM

Re: Sculpting with cement
 
How are you going about it; directly or indirectly? Direct techniques usually involve making an armature, covering it with screen of some sort, and applying concrete mortar to the screen. Indirect techniques require making a mold and casting concrete into it. There are also combinations of both methods that can be used.

Andrew Werby
Juxtamorph.com

Scout 09-04-2014 05:51 PM

Re: Sculpting with cement
 
I'm doing both. I have used my silicone molds with cement but the weight is prohibitive. I try to stay hollow as much as possible. Rebar supports. Fiberglass fibers (although I am using the wrong kind. I am thinking next trying a subtraction method. I am learning lots of lessons. I hope I can remember them all... but having a wonderful time.

Have also explored medium weight cement. Not too bad once you get used to it. Also sculpting with just cement with a few admixes. Can't use the fiberglass fibers with the sculpting because I could not tool it. Had to burn off the fibers that stuck out with a torch.

That's a bunch of prattle but I hope you get some idea of what I'm doing.

Andrew Werby 09-05-2014 02:13 PM

Re: Sculpting with cement
 
You might try using polyester fibers instead of fiberglass. You still can't tool it, but it's nicer to work with. You can mix the fibers into the concrete mortar and apply it to the screen; it adheres nicely without falling through too much. Then follow up with layers of straight mortar, which you can tool.

Yes, weight is an issue with concrete sculpture - it adds up fast. I prefer to do it when the installation's going to be permanent, so I never have to move it...

Andrew Werby
Juxtamorph.com

Scout 09-05-2014 03:04 PM

Re: Sculpting with cement
 
Weight is major. That's why I'm using a medium weight cement mix. I was wondering what the fibers do exactly. This maybe strange but I like to make do. We have a farm and after feeding the cows hay, we have loads of nylon or some kind of plastic webbing. Do you know the kind that comes on the big round bales? Anyway, I was thinking I could cut those up and use them. Any thoughts on that?

Scout 09-05-2014 04:06 PM

Re: Sculpting with cement
 
Never move it... Amen!

Andrew Werby 09-06-2014 03:01 PM

Re: Sculpting with cement
 
Being an urban sort myself, I'm not sure what kind of webbing you've got, but what the heck - give it a try. Anything that gives the mortar something to hang onto should work. Once you've got a solid layer of concrete, you can build it up more. Painting the underlying layers with admix helps promote adhesion, especially if you've let it dry out.

Andrew Werby
Juxtamorph.com

Scout 09-08-2014 10:22 AM

Re: Sculpting with cement
 
Thanks Andrew. Do you think I should cut the webbing into small pieces or lay it in between the cement and mortar. I'm about to do a large piece and I want to use this webbing. I'll let you know how it goes.

Andrew Werby 09-08-2014 05:31 PM

Re: Sculpting with cement
 
I'm not sure what you mean by "lay it in between the cement and mortar". You don't really want to use straight cement anywhere, except maybe as a paint over the final surface; it's all mortar if you're applying it directly. If you're laying it into a mold, you'd put the mortar in first, and back it up with your plastic mesh. If you're starting with an armature covered with screen, then you'd dip the mesh in wet mortar, and lay it onto the wire screen and apply mortar over the top. Cut it into small pieces if your surfaces are complicated, otherwise larger ones will work okay.

Andrew Werby
Juxtamorph.com

Scout 09-09-2014 07:36 AM

Re: Sculpting with cement
 
2 Attachment(s)
So you don't ever use just cement and water except to paint with? Mortar is sand and cement. On this big piece I'm doing, you think I should put the sand and cement mix on the surface of the mold and then the webbing and then heavier cement, maybe a medium weight cement? Then I can fill the rest of the mold with something lighter. Maybe expanding foam?

Have you ever worked with perlite substituted for the rock?

Andrew Werby 09-09-2014 04:01 PM

Re: Sculpting with cement
 
Quote:

Originally Posted by Scout (Post 106063)
So you don't ever use just cement and water except to paint with?

[Not usually; it has low strength and tends to crack.]

Mortar is sand and cement.

[It often has clay, lime, admix, and other ingredients added.]

On this big piece I'm doing, you think I should put the sand and cement mix on the surface of the mold and then the webbing and then heavier cement, maybe a medium weight cement?

[Yes, except put more concrete down before adding the mesh. The problem will be in getting all that stuff to stay on the surfaces of your mold without slumping off. To be honest, that looks like a mold that would work better poured than laid up. A concrete vibrator would help with that.]

Then I can fill the rest of the mold with something lighter. Maybe expanding foam?

Have you ever worked with perlite substituted for the rock?

[Sure, perlite is good stuff, but it tends to suck all the water out of the concrete. Try soaking it a while before adding it (you might have to weigh it down in the bucket, since it wants to float). I doubt that the foam would do much for you in this application. A mixture of perlite, sand and cement would be a better and more compatible filler.]

Andrew Werby
www.computersculpture.com

Nelson 09-09-2014 10:53 PM

Re: Sculpting with cement
 
Quote:

Originally Posted by Scout (Post 106046)
I am trying out cement instead of clay for a while. It's quite the challenge. There don't seem to be any forums for cement so I thought I'd come back here and see if I could get any interest going.

I have been consumed with watercolors for a while but now I need to sculpt again. I am doing life size people.

Does anyone have an interest, or better, any information?

Hi Scout, I ¨ve done a bit cement sculpting, but mostly in Steel. Cement is the most challenging médium in my view, when compaired to metal, Wood, and even Stone. In all, it'll depend on what sort of sculture you wanna get into, Realistic figurative, abstract....? Cement is not forgiving when it comes to time, so dealiing with details to a realistic level takes in my view too much effort and time. As to achieving more efficiency, abstract figurative is easier.... for monetary purposes I´ve gradually switched to sculpting rocks, faux bois and other artisian stuff that sells better, though I still enjoy much the creative process. Hope you find your niche of work or even as a hobby.

Scout 09-10-2014 07:18 AM

Re: Sculpting with cement
 
Ok Andrew, I'll try soaking them first.

Hi Nelson. I haven't been here lately. Been into other art obsessions. Right now I'm into cement. I am going to build, I almost said pour but it's building building building, Andrew with his Cats today.

I actually did pour this one before. It was very heavy. So this time I'm trying medium weight cement of various ratios. Tell me your experiences with the way cement is mixed. I do a mortar mix on some of my smaller casts, I like the marbly effect drying it fast gives it.

Any advice you might have or thoughts on the process, I would love to talk about them with you.

I intend to pack the two halves of the mold instead of pouring it put together. At least tell me the problems you ran into with cement. Tell me a bit about additives. I'm using an Acrylic mortar admixture.

Andrew Werby 09-10-2014 03:40 PM

Re: Sculpting with cement
 
You don't want to dry concrete fast; that degrades its ultimate strength. Wait a week or so before unmolding it, if you don't want to lose fine details. And keep it as wet as possible as long as possible afterwards; it supposedly doesn't achieve its full strength until it's been submerged for 7 years. If you can't submerge it while it cures, try wrapping it in burlap and wetting the cloth periodically.

Andrew Werby
Juxtamorph.com

Scout 09-14-2014 02:51 PM

Re: Sculpting with cement
 
If I leave it too long, I can't tool it. What is dry pack? Is it just moist sand and cement mix? Dryish mortar? Is that how they make cement blocks?

Andrew Werby 09-14-2014 03:07 PM

Re: Sculpting with cement
 
If you want to tool it as it sets, I'd think a direct method would be better than casting into a mold. The surface of a cast piece when it sets against the mold is different from the interior surface; your tooling efforts would expose the more porous material underneath. So if you don't remove the whole cast surface, it would look uneven and blotchy. If your mold and casting technique are good, you shouldn't need to work the surface further after unmolding.

"Dry pack" is barely-moist cement and sand, mixed about 1 to 4. I've used it for setting tile on, but haven't thought about using it for sculpture. It's not too hard to get it flat, although I'm not sure how well it would work directly, since it doesn't have much strength or cohesiveness. But I suppose you could pack it into a mold.

I'm not sure how cinderblocks are produced; I imagine there are a few different processes to do that.

Andrew Werby
Juxtamorph.com

vikkilynn 09-28-2014 11:30 AM

Re: Sculpting with cement
 
I have done quite a bit of cement sculpting. it was fun and challenging. I used tomato cages, drywall wire or screen. after I made the bottom I would put them on flat dollies so I could move them around easily. I got lots of info from this garden art site which has posters who work in concrete, hypertufa and faux bois.
http://www.thegardenartforum.com/php...321935eb704134

Scout 09-29-2014 12:28 PM

Re: Sculpting with cement
 
Thank you for your responses. I am working on it and will get back when I have something to show.

Thanks for the link!

Nelson 10-18-2014 08:47 PM

Re: Sculpting with cement
 
Quote:

Originally Posted by Scout (Post 106066)
Ok Andrew, I'll try soaking them first.

Hi Nelson. I haven't been here lately. Been into other art obsessions. Right now I'm into cement. I am going to build, I almost said pour but it's building building building, Andrew with his Cats today.

I actually did pour this one before. It was very heavy. So this time I'm trying medium weight cement of various ratios. Tell me your experiences with the way cement is mixed. I do a mortar mix on some of my smaller casts, I like the marbly effect drying it fast gives it.

Any advice you might have or thoughts on the process, I would love to talk about them with you.

I intend to pack the two halves of the mold instead of pouring it put together. At least tell me the problems you ran into with cement. Tell me a bit about additives. I'm using an Acrylic mortar admixture.

Hi Scout,
this my email

ironywood@gmail.com
email me and I´ll be glad to talk with you. ciao.

Scout 12-02-2014 12:03 PM

Re: Sculpting with cement
 
Hello, I'm still working in cement. I made some smaller pieces. I want to paint them with a wash and then a dry brush technique. How long does a small piece ( maybe about football size) have to cure before painting? I can leave the bottom unpainted if it needs it. Thanks for your help.

Art-Deco 12-05-2014 12:59 AM

Re: Sculpting with cement
 
The concrete should be kept wrapped in a plastic bag or the like and kept wet/damp in it for 5-7 days then it can be removed and let air dry.
Most paints seems to say allow new concrete to cure for 30 days (or longer) before painting

Andrew Werby 12-05-2014 04:44 PM

Re: Sculpting with cement
 
I think the concrete has to be dry before you paint it with regular house paint. But if she just wants to brush pigment onto it, that can happen when it's newly set or soon afterwards. Mixing a little neat cement into the lime-proof pigment (you get that at the concrete supply store) will give it some body.

Andrew Werby
Juxtamorph.com

Scout 12-06-2014 10:14 AM

Re: Sculpting with cement
 
Thanks. These are small things I sculpted molded cast and now I want to add some acrylic paint. Do I need to prime it with something thinned down?

Andrew Werby 12-06-2014 03:25 PM

Re: Sculpting with cement
 
If you want to use acrylics, then Art Deco's advice should be followed. You'll want the piece to be thoroughly dry before applying them, and priming would be a good idea. If you use a white-pigmented shellac (BIN, etc.) then you can thin the first coat with denatured alcohol to insure better penetration. But follow that up with a few full-strength coats to give yourself a good surface to paint on.

Andrew Werby
Juxtamorph.com

Scout 12-14-2014 01:57 PM

Re: Sculpting with cement
 
Here's a different question. How critical is the sand, in it's cleanliness? We have lots of sand on our place, all colors. Seems to me that if I sift it, it ought to suffice.

We also have red and white clay. Can I mix it into the cement to make it creamier to sculpt with? Anyone have a recipe for sculpting cement?

Art-Deco 12-14-2014 09:45 PM

Re: Sculpting with cement
 
Quote:

Originally Posted by Scout (Post 106318)
How critical is the sand, in it's cleanliness? We have lots of sand on our place, all colors. Seems to me that if I sift it, it ought to suffice.

Make sure the sand is not somehow contaminated by sea salt if you are anywhere near the ocean, there was salt water near by, or this sand had been trucked in and placed there for "fill" or something.

Years ago a friend in Oregon got a load of sand that apparantely originated from the coastal/beach area, turned out it was contaminated by salt from salt water and his concrete turned out very poor. If in doubt buy some bagged sand if you don't need lots of it

Scout 12-15-2014 07:43 AM

Re: Sculpting with cement
 
We are in So. Ga. I doubt there is any salt in our sand. I'm going to try it. I'll let you know how it goes.

Did anyone have any experience with clay in cement? Plaster in cement?

Art-Deco 12-15-2014 01:50 PM

Re: Sculpting with cement
 
Quote:

Originally Posted by Scout (Post 106323)
We are in So. Ga. I doubt there is any salt in our sand. I'm going to try it. I'll let you know how it goes.

Did anyone have any experience with clay in cement? Plaster in cement?

I use the fine white Unimin quartz sand in the bag, it's perfectly clean, dry, free of any foreign material, it comes in 50# plastic bags. I prefer this over trucked in sand which is always wet or damp, and if dumped outside- cats, leaves and debris become an issue, if it stays there long enough you get grass or weed seeds sprouting quickly and their roots create a headache to sift out.
I'm trying to move away from concrete in favor of terracotta.

Clay I doubt will help anything, and likely make weak concrete, if you put plaster in concrete you essentially get USG's Hydrocal or Hydrostone gypsum cement. USG's spec sheets show that they add Portland cement to the gypsum but not the exact amount.

I can say from tests that neither Hydrocal or Hydrostone last outdoors, you get this after about 3-4 years, they weather and disolve away like sandstone rocks in the Utah desert have:


Duck 12-15-2014 01:50 PM

Re: Sculpting with cement
 
Quote:

Originally Posted by Scout (Post 106318)
Here's a different question. How critical is the sand, in it's cleanliness? We have lots of sand on our place, all colors. Seems to me that if I sift it, it ought to suffice.

We also have red and white clay. Can I mix it into the cement to make it creamier to sculpt with? Anyone have a recipe for sculpting cement?

Dirty sand might actually give you more of a paste (brittle too). Most concrete/masonry suppliers will have both Sharp and Mason sand. Mason sand is washed and round. Sharp is washed and flat and mostly used in ready mixed concrete. I’ve read through what you’re doing and I think the round mason sand mixed very poor 8-1, 12-1, and add a bonding agent (Elmers Glue) might give you more time to work. Try it without the glue too, it will be soft enough to carve (detail ??). Paint it with watered down acrylic paint the next day. let that set for a few days and stiffen/harden the sculpture with a good acrylic satin or gloss concrete sealer.
......hope it works :D




http://lawrenceduckworth.com

Andrew Werby 12-16-2014 05:17 PM

Re: Sculpting with cement
 
Ditto what AD says about the salt. But a little clay's not a problem; most mortar mixes have some fireclay in them to impart plasticity. Sharp sand is best for building up directly; round sand flows better for casting. A little gypsum plaster will make the concrete "kick" faster, which can be helpful at times. I didn't know Hydrocal or Hydrostone contained Portland cement; if they do it can't be very much, since they act a lot more like plaster than concrete. USG's Gardenstone has quite a bit, so it lasts better outdoors.

Andrew Werby
Juxtamorph.com

Scout 12-16-2014 07:24 PM

Re: Sculpting with cement
 
Yes, I did know about plaster, melting, in the rain over time. I use plaster for mother molds. I was using plastipaste but it is so expensive.

I have heard that, like you say, plaster added will set up faster. I have tried many ways. It seems depending on the application and size, one can mix cement in most any ratio, to many aggregates or sand or perlite etc. As long as I let it set long enough, it is fairly strong.

Do you think it is necessary to weld the rebar or just tie it on say something about 8 feet tall.

Art-Deco 12-17-2014 01:16 AM

Re: Sculpting with cement
 
Quote:

Originally Posted by Andrew Werby (Post 106327)
I didn't know Hydrocal or Hydrostone contained Portland cement; if they do it can't be very much, since they act a lot more like plaster than concrete.


I meant hydrostone, ultrastone and duracal have Portland, not hydrocal, it even says "Warning: contains Portland cement" on the bags, the exact ingredients are in the MSDS:


HYDROSTONE

Plaster of Paris, & Portland Cement

Plaster of Paris >90%
Portland Cement <5%
Crystalline Silica <5%

http://shop.clay-planet.com/MSDS/pla...%20Plaster.pdf


Ultracal 30

Plaster of Paris >85%
Portland Cement <10%
Crystalline Silica <5%

Ultimately it appears the difference between those two are Ultracal has a little more Portland added to it, and they have less than 5% and 10% Portland respectively, so in a 100# bag the hydrostone has a little under 5# of Portland, Ultracal a little under 10#. It also looks like you can take Plaster of Paris and add up to 10% Portland to it at home, more than that and I guess it acts more like concrete- taking hours to set up and days to fully cure.
Ive used hydrostone and ultracal, they stay syrupy liquid and then suddenly and rapidly harden up, very unsuitable for hollowing out a large cast since they have almost no plastic stage where you can work and mold it.

Andrew Werby 12-17-2014 04:12 PM

Re: Sculpting with cement
 
That makes sense, about the Hydrostone. Whether to weld or just tie the rebar really depends on the configuration of the armature you're trying to build. If it's pretty simple, tying can work, but as things get more complex and the forms more extended, it helps to be able to weld the connections.

Andrew Werby
Juxtamorph.com

Scout 12-30-2014 04:21 PM

Re: Sculpting with cement
 
We are about to buy a welder. Any suggestions?

Chris_Johns 12-31-2014 09:53 AM

Re: Sculpting with cement
 
Quote:

Originally Posted by Scout (Post 106343)
We are about to buy a welder. Any suggestions?

If you are mainly wanting it to weld armatures together I would suggest looking mostly at MIG welders. These tend to be the most convenient for assembling complex structures, especially if you are doing a lot of tacking and welding of relatively thin rod, bar and plate. It's also the easiest process to learn for most people.

I would stay away form the very cheap end of the market but there is also no real need to spend a lot on a big brand industrial model either.

A good general indicator of quality is the duty cycle, and check whether figures quoted are at the maximum operating power. 160 to 180 amps should be more than adequate for most jobs as long as the duty cycle is ok. Something like 35% or more at full power is fine. Beware that some of the cheaper manufacturers quote duty cycle figures in a way which, if not factually incorrect, is a bit misleading.

Models with digital control which automatically matches the wire speed to the voltage is useful and saves time but is not essential and in general inverter based machines tend to be a bit easier to use than transformer based ones. In terms of buying I would look at specialist welding suppliers rather than the more general purpose tool retailers.

A stick welder is the other alternative and they do have the advantage that you don't need to worry about gas bottles, and are a bit cheaper to buy and run, but for the type of work you are talking about they are likely to be less easy to use, especially if you're not an experienced welder.

Something else to look out for is the ability to reverse the polarity, this allows you to use flux-cored wire which behaves in a similar way to stick welding. It tends not to be as neat or easy to use as gas shielded welding but can be a useful standby if you run out of gas and performs better outdoors (as well as making the machine more portable) and copes better with welds where it is impractical to properly clean the joint.

You can now also get multi-process machines which will do MIG, stick and DC TIG in one package (although in some case you may need additional accessory kits to get the full functionality). These are worth considering is you think you might do a wide range of different processes but are a bit more expensive than the single use machines of equivalent quality.

It can also be good to get a machine with a detachable torch assembly. The torch parts do need occasional maintenance and part replacement and this is more difficult on the hard-wired torches. But not a deal breaker is you just want an economical machine. It also makes life much easier if you ever want to weld aluminium.

The high end machines will tend to have features that you won't really need for small scale jobbing work and these tend to be geared more towards increasing productivity on industrial production rather than actually producing better welds.

Personally I would go for a mid-priced inverter based machine from a reputable brand, with MIG welders it is definitely worth spending a bit extra to get a decent mid priced machine as opposed to the budget models.

Scout 01-01-2015 09:02 AM

Re: Sculpting with cement
 
Thanks Chris. All good information. What do you suppose a mid range welder should cost. It will also be used to weld on farm equipment. Not big jobs but not piddly either.

Chris_Johns 01-01-2015 11:01 AM

Re: Sculpting with cement
 
I can't speak specifically for good brands in the US but I would look at something like this :

http://www.r-techwelding.co.uk/weldi...R-Tech_IMIG180

In UK prices I'd expect to pay around £400-£500 and pound to dollar prices equivalents often work out at around 1 to 1. That one can also be used as a stick welder which might come in useful for farm repair work.


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