terrim8 Posted December 30, 2018 Report Share Posted December 30, 2018 I am making a large mold using one of those large plastic buckets that you get from the hardware store. The model fits well except it only has about an inch around the sides for one small portion. I have heard that hydrocal (plaster w a bit of portland cement) is stronger than pottery plaster No.1 and I'm wondering if I should use this because of the thin area. Anyone know? Does it adsorb the casting slip as well as pottery plaster No.1? (The store that sells it isn't open 'till Jan8 so I can mull it over till then.) Link to comment Share on other sites More sharing options...
JohnnyK Posted December 30, 2018 Report Share Posted December 30, 2018 The 1" thickness using pottery plaster shouldn't be a problem unless you drop the mold, but for everyday use the PP should be OK. How many pieces do you plan on casting in this mold? Link to comment Share on other sites More sharing options...
terrim8 Posted December 30, 2018 Author Report Share Posted December 30, 2018 depends on how well the mold comes out! I'm not thinking about how many yet- just trying to get 1! So are you inplying that hydrocal will last longer??? Link to comment Share on other sites More sharing options...
Mark C. Posted December 30, 2018 Report Share Posted December 30, 2018 I could have this wrong these guys are the experts -USG https://www.usg.com/content/usgcom/en/products/industrial/art-statuary/hydrocal-white-gypsum-cement.html Link to comment Share on other sites More sharing options...
terrim8 Posted December 30, 2018 Author Report Share Posted December 30, 2018 the drying instructions are pretty important from the looks of it. The plaster course I took last summer was at the height of the heat and the fans were going like mad. Looks like I have to try to replicate that. Link to comment Share on other sites More sharing options...
Stephen Posted December 30, 2018 Report Share Posted December 30, 2018 I made a couple of sets of adjustable cottle boards and it was not a big deal and might be easier to work with than the bucket. Youtube prob has a few videos. You can also use ceramical which is strong and about $15 for 50lbs. Link to comment Share on other sites More sharing options...
Chilly Posted December 30, 2018 Report Share Posted December 30, 2018 From my understanding of making casting moulds, the thickness is to do with even casting as much as strength. A thin wall will get saturated with water from the slip more quickly than other thicker walls in your mould. This might or might not be a problem, depending on the overall size of the mould. Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted December 30, 2018 Report Share Posted December 30, 2018 If you need a round support for your mould, you can also use flashing strips from the hardware store. The diameter is adjustable that way. Link to comment Share on other sites More sharing options...
terrim8 Posted December 30, 2018 Author Report Share Posted December 30, 2018 Sounds like I should try a slightly wider mold - have to go check out the hardware store for flashing or a crazy carpet. I'll keep the buckets for slip. One more question : will paper-plaster mix leave holes where the paper slurry bits are? I'm also trying to reduce the weight of this thing. But I have to keep the mold surface smooth, so that is another decision to make before the store opens next Tuesday - Calgary is such a one horse town - no instant gratification here! Link to comment Share on other sites More sharing options...
Roberta12 Posted December 30, 2018 Report Share Posted December 30, 2018 27 minutes ago, terrim8 said: Sounds like I should try a slightly wider mold - have to go check out the hardware store for flashing or a crazy carpet. I'll keep the buckets for slip. One more question : will paper-plaster mix leave holes where the paper slurry bits are? I'm also trying to reduce the weight of this thing. But I have to keep the mold surface smooth, so that is another decision to make before the store opens next Tuesday - Calgary is such a one horse town - no instant gratification here! When you get this sorted out, I would love a photo. I am having trouble visualizing. And I made a bunch of plaster molds this summer. In the heat,wind,sun. I am impressed that you are doing this in the winter!! Link to comment Share on other sites More sharing options...
terrim8 Posted December 30, 2018 Author Report Share Posted December 30, 2018 31 minutes ago, Roberta12 said: When you get this sorted out, I would love a photo. I am having trouble visualizing. And I made a bunch of plaster molds this summer. In the heat,wind,sun. I am impressed that you are doing this in the winter!! Will do. New Year- New Project I even considered using an ice form as the model but first things first- get the basic process done. Link to comment Share on other sites More sharing options...
Stephen Posted December 30, 2018 Report Share Posted December 30, 2018 I think I might be confused and of course both ceramical and cottle boards would not be of any value for a slip casting mold. Link to comment Share on other sites More sharing options...
Roberta12 Posted December 30, 2018 Report Share Posted December 30, 2018 1 hour ago, terrim8 said: Will do. New Year- New Project I even considered using an ice form as the model but first things first- get the basic process done. That is an interesting idea! I wonder if the plaster, when it is heating up, would melt it's mold??? Hey, let me check airfare to Calgary....I gotta see this! r Link to comment Share on other sites More sharing options...
terrim8 Posted December 30, 2018 Author Report Share Posted December 30, 2018 I don't know about airfare but our dollar is in the tank right now - floating upside down. So things would be cheap for you on this side of the border. Have to sort out the process though. The ice would melt & maybe with some crazy shapes! Maybe a process where I can get the hardening rate of the plaster to be a tad faster than the melt. More hair brained ideas to keep me experimenting Link to comment Share on other sites More sharing options...
terrim8 Posted December 30, 2018 Author Report Share Posted December 30, 2018 2 hours ago, Stephen said: I think I might be confused and of course both ceramical and cottle boards would not be of any value for a slip casting mold. Cottle boards are used and I have some, but this item is bigger than my boards , so I've had to find something else. Just picked up some crazy carpets at the hardware store - (the kid's tobogganing plastic sheets). They are stiff enough to form a wall around my model. Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted December 30, 2018 Report Share Posted December 30, 2018 When I saw Trudy Golley give a paper plaster demo a long freaking time ago, she did a skim coat or a milk coat of regular plaster over the master before adding a subsequent layer of paper plaster. That way you don't get the texture on the working surface if you don't want it. Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted December 30, 2018 Report Share Posted December 30, 2018 2 hours ago, Roberta12 said: That is an interesting idea! I wonder if the plaster, when it is heating up, would melt it's mold??? Hey, let me check airfare to Calgary....I gotta see this! r You can stay at my house and we'll both go help her. We're having ham and pretzel buns for New Years dinner. Link to comment Share on other sites More sharing options...
terrim8 Posted December 31, 2018 Author Report Share Posted December 31, 2018 Ah ha! I was thinking about that- doing a skim coat but the trick would be to get it on evenly. I should contact her about this. Looks like I'd better soak some paper . Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted December 31, 2018 Report Share Posted December 31, 2018 When she did it, she flicked wet plaster with a gloved hand onto the master she was using, creating just a fine enough layer that the inner surface of the mould was going to be smooth. As soon as she finished the milk coat, she started mixing the paper plaster to apply over top of that. Link to comment Share on other sites More sharing options...
terrim8 Posted December 31, 2018 Author Report Share Posted December 31, 2018 mmmmmm pretzel buns ..... and my first try with ice Link to comment Share on other sites More sharing options...
terrim8 Posted December 31, 2018 Author Report Share Posted December 31, 2018 Link to comment Share on other sites More sharing options...
Mark C. Posted December 31, 2018 Report Share Posted December 31, 2018 Why and what are using the ice for?Never heard of that in plaster making ???? Link to comment Share on other sites More sharing options...
terrim8 Posted December 31, 2018 Author Report Share Posted December 31, 2018 Because of the ease of creating ice models from various types of molds in our climate, many people experiment with this. An extreme end member of this activity is ice carving competitions and ice "hotels". The less experienced artists use ice molds - homemade or purchased silicone molds. You've probably seen the floating ice centre pieces used in punch bowls or the ice lanterns along walkways into homes. Plaster mold making is a new-ish thing for me and I like to see what is possible while learning how to use this material. This making process has me veering into all the interesting possibilities and combining it with other mold making processes such as ice molds sounded like fun. This involves experimenting with types of plaster to use - hydrocal or pottery plaster No.1 or paper plaster. Then seeing if you can use ice as a model and testing to see if the plaster then can dry well for slip casting. My first experiment last night proved a simple ice form can work. Too many bubbles in the plaster so that needs work - but its a start. I'm still making the large model and mold, using a crazy carpet that's wider than the plastic bucket & I'll use the paper plaster to make it lighter - but still haven't decided on pottery plaster no.1 or hydrocal. As usual, I'll probably choose the less expensive option first. I'll run the ice -plaster experiments on a very small scale (paper cups) at the same time until I get it working. The crowd sourced input helps - like being in a room with everyone's experience! Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted December 31, 2018 Report Share Posted December 31, 2018 @Mark C. as a for instance, if you want the inside curve of a plastic or metal bowl for a slump mould, you can fill it with water and throw it outside overnight for a quick and dirty master to make the mould with. Link to comment Share on other sites More sharing options...
Mark C. Posted December 31, 2018 Report Share Posted December 31, 2018 Ok I see its a climate like a deep freezer.I get it now Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.