View Full Version : CAVE SET. What do I use

08-10-2009, 02:50 PM
I am doing a low budget film, somewhere in the $150,000 range and need an idea on how I can do a really large int. cave set for low cost. I was thinking of doing it with a lot of paper mache. I have done test and the end result looks good.

Is this the best way to do it for low cost or does anyone know of another way.

Has anyone done a cave out of paper mache and how did it turn out??? Any help would be great.



08-10-2009, 03:12 PM
That's a tough set. My gut would say go shoot in an actual cave. Do they have caves in Utah? I would think it would be less of a headache to see if you can find a cave for a day to shoot at and just rent some generators, but that may be me being ignorant. One thing I saw on the BTS footage of Lord of the Rings was the way they made rocks and cliffs. Pieces of foam banged up and painted then put on wooden walls. It strikes me as cheaper and faster then paper mache. Not only that but the genius of it was they were on rollers, so when it needed to look like they had been walking in the cave for a while, they would just rearrange and re-light the same pieces to look different. Just an idea. Let us know what you decide and if you could post pictures. I am curious how you hurdle this task.

Sad Max
08-10-2009, 03:16 PM
The largest cave sets I've done were for Star Trek (mostly staff shop vacu-form rock sheets over wooden framing) and for Lost (plaster over wood and chicken wire support).

Never tried paper mache but it sounds like it ought to work. Depending upon your scripted action perhaps you could build a small set piece and get the rest of the cave via digital set extension.

Ryan Patrick O'Hara
08-11-2009, 03:04 AM
If you need a small cave, I've shot some cave footage inside really big mini golf places. there is always a cave in the big ones. Worked out almost ridicuously well. Of course we had to tarp the ground (green) and then add sand, dirt and etc on top. But none the less, it worked.

08-11-2009, 07:40 AM
Mini Golf Course might be a good idea, but the set has to be pretty large. We have a studio all ready that we can build the set in. We thought of using a real cave, but we are having trouble getting permits to do that because most are part of the national parks service up here and they don't want big lights and other things that could cause damage to the caves. Right now I think our best option might be to use paper mache cost wise, but it will take a lot of time to make them out of paper mache.

Thanks for some suggestions. Any other ideas?


08-11-2009, 07:51 AM
Sad Max's plaster over wood and chicken wire is the way I'd go. It may cost a bit more than paper mache but I think it would take a lot less time and would be closer to the texture you need. I'd use rough plaster and Plaster Weld to help it adhere to the wood. I would NOT use any gypsum or other accelerator in the plaster.

08-11-2009, 02:29 PM
are you talking big like the cave scene in the new Harry potter movie?

any reason you're not shooting a green screen?

08-12-2009, 09:26 AM
Not as big as the Harry Potter set, but I do really like the look of it. I think we would be about half that size at least.

08-12-2009, 09:29 AM
Green Screen is an option. We do have access to a green screen that is about 40 high by 50 feet wide, so it is an option. We will be shooting this with a Red Camera. I have never shoot on Green Screen with a Red. Does anyone know of any problems shooting green screen with a Red?

Sad Max
08-13-2009, 03:06 PM
'Really large' isn't actually the kind of description that yields meaningful estimates.

What square footage do you require, how many walls of what height, with what kind of finish laid on top of them, with how large a budget and in what kind of time frame delivered to what particular location?

Given most if not all of the answers a Construction Coordinator or Foreman can quote you estimated dollar figures and/or important schedule + budget considerations. Plus that's all useful information to a bunch of other departments who will need it and may as well get it up front.

Free advice, guaranteed your money's worth.

08-13-2009, 04:41 PM
I've never shot red but I would imagine it shoots GREAT greenscreen.

That I think is by far your best option
esp since a cave is dark.
It's way easier to sell a dark, out of focus cave wall that a spectacular landscape.
digimatte is your best friend on this.

08-13-2009, 06:32 PM
Take a look at the Behind the Scenes from the horror film, Descent. The majority of the story takes place inside an extensive cave system so they built all sorts of tunnels and passage ways. It's well worth looking at to gather ideas. The main thing, use darkness. It's your friend.

08-14-2009, 10:01 AM
Yeah, I will take a look at those videos. As far as size goes that hasn't been totally decided yet. I think they are going to be somewhere around 6000 sq feet. Maybe even a tad bit bigger.

Sad Max
08-14-2009, 10:05 AM
You can probably save yourself a lot of time and $$$ working out your requirements in previs, so as to know exactly what you really need to build.

08-18-2009, 12:25 AM
I'll give a +1 on checking out the Behind the Scenes for "Descent". One thing you'll find is that their largest set piece was redressed slightly and relit to act as several different sections of the cave system, giving them the biggest bang for their buck.

08-20-2009, 07:04 AM
Thanks, guys for all the help and the ideas. I ran a test the other day with Paper Mache on a small scale. I just wanted to first of all see if I could even make paper mache look like a rock. Well I made a rock in about a hours time, that doesn't include the drying portion of the paper mache. The paper mache took about 6 hours to dry, but time on the project was about an hour. I was impressed with how the rock looks. It looks really well. I am going to post some pictures sometime soon so all can see. Thanks again.

08-20-2009, 09:58 AM
Something that might be faster and is certainly stronger is urethane foam. You need to get someone to come in and do it but we used to do some really big set pieces with the stuff. You build a chicken wire mesh and yet some kind of backing on it, strips of paper cloth, pretty much anything that will keep the foam from spraying right through the mesh. We had the machine but you can probably find a place localy that has one. It's basically a big mastic spray gun loaded with structural foam. This isn't the soft foam that you get for insulating homes, it's VERY hard when it cures. You need to have someone who knows what they are doing because this stuff can be dangerous. It sticks to anything and the two parts uncured are toxic. It ends up like molded masonite, very hard and much stronger than one would think. It will end up being pretty smooth so you will still probably need to do some treatment but one person could probably spay the while cave in a day or less and it would be cured by the time they cleaned up. A 6K Sq foot cave of paper mache is going to take forever to dry and your going to need a lot of structure to hold all the weight. And of course there is the fire issue. Your probably going to have some pretty hot lights in there and paper burns quite well.

Sad Max
08-20-2009, 10:03 AM
Spray foam is a big-money approach. If you have the $$$, sure, go for it.

Don't forget to budget for sealing/finishing, too. You'll definitely want a paint finish and probably a seal coat, too.

08-20-2009, 10:46 AM
Spray foam is a big-money approach. If you have the $$$, sure, go for it.

Don't forget to budget for sealing/finishing, too. You'll definitely want a paint finish and probably a seal coat, too.

Not sure where you are pricing this but we used this for theatre sets and a HUGE opera piece, neither had big $$$. With paper mache you are talking about having to build serious structure to hold the weight and weeks of applying it and probably many weeks of drying, unless you bring in big heaters and then you have that cost. If time is no problem and your labor force is free then maybe you save on the paper. And you certainly don't need any sealing and you have to paint any way you go unless the cave is supposed to be made out of paper. In fairness I don't think your talking about the same material I am. If you tape up a 4X8 piece of butcher paper and spray it with this stuff you end up with a 1/4" sheet of plastic you can walk on with very little support, We did a hat that was like 15' in diameter and you could clime on it with no internal structure at all. It's not cheap but it's about the same as the other solutions providing your paying for labor and supplies. And I'm not even sure you could do the overhead portions with mache with out doing them inverted and flipping them into place after they dried.

And for a short trip to reality. 6,000 sq ft cave. Lets assume it's a cylindrical tunnel, well the top 1/2 anyway. So if we for arguments sake make it 30' wide that makes it 200' long. That gives you a cave surface (not counting the floor) of around 9,400 square feet. Wet mache weighs around 1.5 to 2lbs (assuming about a 1/2" layer) which comes in at around 9 tons (18,000 lbs). Your going to have to build outside structure to hold it up after it dries and some serious internal structure to hold that weight while it's wet. I don't think this is the low $ spread.

Sad Max
08-20-2009, 10:49 AM
A 1/2" thickness of paper mache is excessive. 1/8" is adequate, and you build in sections. This is not a just-run-at-it proposition; this ought to be modeled and planned in lifts, to start with.

I'm thinking back on the experiences of building large cave sets for Lost and Star Trek for which we variously used spray foam, spray concrete, plaster/jute and vacuformed materials.


08-20-2009, 12:34 PM
I agree with you but you did read the OP right? He does not have your experience nor anywhere near the budgets your talking about. And if he's making rocks to try it out then he doesn't have the kind of crews your talking about either. 1/8" would help weight wise but also have no structural integrity at all so now you are talking serious structure. In his price range I don't think he's going to have a bunch of lifts around either. But you know we are both speculating a bit here.

So OP, what level of large structure set building experience do you have?

08-20-2009, 12:49 PM
Actually to add some questions to the OP.
What are they giving you for a budget, aprox. And how large and experienced a crew do you expect to work with. And do you have any idea how much you can avoid building? IE you probably don't need a ceiling on most of it IF the cave is supposed to be really tall.

08-20-2009, 01:18 PM
All very good questions. Thanks again for the info. This has been a very interesting position that my producer has put me in. I have no set design background at all. He just threw out the idea of paper mache so I just asked the question. I am a Director of Photography and Camera Operator.

Right now I have a crew of about 8. We have a couple of Props guys that are really good, that think the paper mache is possible. They have done a lot of play set design in the past and said that worked great. They just have never made a cave out of the stuff, so we are all good friends so I had some time on a Saturday and just put it together. I think it would be very possible, but time consuming to use paper mache. I don't think the walls need to be really strong, we are not climbing on these cave walls. I do agree with the lights. They do get really hot and that could cause some issues. We do have a gaffer that has a ton of equipment. He even has these lights that don't get hot that light really well. So maybe that wouldn't be an issue. Plus I think I like the idea moving walls around to look like a different set, plus using different camera positioning we could cut down on the size of the caves.

As far as budget goes I don't know what we are getting for set design, but I would say half of the film will be in these caves.

Right now we are talking about a $160,000 budget for the whole movie, so it is pretty low budget. That needs to of course pay everyone "Crew and Cast" as well as a red rental and other things like food and other film equipment.

So like I said I was just interested in the way people would go with this. I have no background in this stuff, but I am a very creative guy and that's why I ran the test for the Producer.

Because we are so low budget I would be putting in time to help put these sets together. We all play multiple rolls in our production group. Thanks again keep the feed back coming.

Sad Max
08-20-2009, 01:44 PM
FWIW lifts here doesn't mean equipment; it means prefabricated sections of a large set piece that are built individually, then joined together in place.

08-20-2009, 01:51 PM
You have to think like a filmmaker...

I went to the Utah Film Commission web page and came up with this.


Put in search terms for mine or cave...

If you can't actually shoot the interior scenes in there, you can shoot the exteriors and "sell" the size and scope...

08-20-2009, 04:42 PM
FWIW lifts here doesn't mean equipment; it means prefabricated sections of a large set piece that are built individually, then joined together in place.

AH, I've done a lot of set design and construction and trade shows and such but not art direction so I missed the term. You would probably need fifts though to get the lifts into place if your walls go very high up ;~).

Since your looking for ideas given your situation I would probably go with cloth soaked in a stiffener (as simple as startch or supper cheap latex paint (we used to toss all the leftovers in a drum and that became dark grayish "rat paint", used for priming etc)) and applied over chickenwire. You might have to stiffen up the lower part s where people actually touch. It will give you a light very paintable skin that will dry faster than mache and be a bit more flexible/ strong. Its also easier to fireproof if nec. You can usually get used sheets at places like The Goodwill that are very cheap. I would contact a manager and get to the warehouse and make a deal on the stuff that they are going to sell as rags. Even if you go with something more substantial lower down this can work well for the upper reaches. Between scrunching the chicken wire and scrunching the cloth you should be able to get very close to a finished look. I would also color the stiffener to be your base color for the rock.

Also your a DP so you know there will only be a fraction of the cave that gets a close look. Find out which parts those are and spend your budget making them look good, some of the rest probably wont need more than the dark undercoat.

08-20-2009, 10:40 PM
Cheapest option is indeed Green Screen. However whether you build a set or use Chromakey, you #1 key tool is LIGHTING. Creative lighting covers all the flaws. I visited the Star Trek set once and was amazed how cheezy it was in open work lights. The magic is created with the creative lighting. Shadow is your friend.