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AndreaB

Slip Casting Moulds

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Good morning, 

 

Here I am again consulting the experts.

 

I have an order for four mugs, they are to be the same and done in porcelain. I'm not at the stage where I can throw semi-identical items. So I thought I'd throw the form that they like and then cast a mould and use porcelain slip.

 

Here's the problem. I've looked at a lot of youtube videos about making moulds and they involve a lot of work.  My thinking is that I build a containment area out of tiles. Press the form half way into clay. Fill the remainder with plaster of paris. Then repeat for the second half.  As the sides are identical no need for registration marks.

 

Are my thoughts incorrect? 

 

Does the mug have to be leather hard or bone dry?

 

Oh and the thrown mug has curves but no handles. Thought I'd cast those as well and slip them together.

 

Your thoughts and advice would as usual be most appreciated.

 

Have yourself a productive but relaxing day.

 

Andrea

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I personally would not go thru the work of mold making for 4 mugs

The idea of mold work is to make many items of the same item. It's a lot of work to make a mold.

Now as to the how of mold making you cannot have any undercuts so theoretically you could do a two piece mold if the form is perfect with a flat bottom. You make another mold of a handle and add that when they are still just right with slip.

It will be easier to make a wood or plastic jig of the mug profile and you throw a cylinder .you press this to shape as the wheel spins which creates you form perfectly. Much easier than making a mold for 4 items.

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You do need the registration marks.  They align the two halves of the mould together while you pour the slip in.

 

But, as Mark C says, too much effort for just four mugs.

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Making a good mold is not easy. You will get all sorts of problems from cutting corners. They do involve lots of work.

 

Making four close-enough mugs will be easier to make with the wheel. You could try to make the mold if you have extra time-- it will teach you something!

 

I haven't made a mold and I don't really plan on doing it. I have watched someone else who worked entirely with slip casting go through the process many times. The devilish details are important.

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You could make mugs from a slab of clay as well around a form and slip off before it dries and make them the same ( close enough)

Add a bottom and handle.

Not wheel thrown but will work fine.

You could extrude them as well fron an extruded if you have access to one.

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Just smiling re. posts about moulds and molds, not about to say anything but misuse has occurred in 2 posts

ANd another post has discolouration which may in fact be mould from the mold . MuY advise is to wash the mugs, not just the insides..

May be better time wise to just throw a lot of mugs and pick out the most similar, if the client is after identical..but chose you to make mugs, can't see the client's reasoning other than she likes your work so go throw mugs and let him select from a few... may not want them identical

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Just smiling re. posts about moulds and molds, not about to say anything but misuse has occurred in 2 posts

ANd another post has discolouration which may in fact be mould from the mold . MuY advise is to wash the mugs, not just the insides..

May be better time wise to just throw a lot of mugs and pick out the most similar, if the client is after identical..but chose you to make mugs, can't see the client's reasoning other than she likes your work so go throw mugs and let him select from a few... may not want them identical

 

Did anyone misuse the mould/mold word? I've always though that "mold" is used in the US and "mould" used everywhere else and both words mean the form(ing) of an object, the growth of the black stuff and moulding trim. Maybe the spelling has changed over the years?

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Mold= to form

Mould= fuzzy stuff on bread

 

If you can throw a reasonable cylinder, try setting up a pointer or a gauge. All you need is a pointy stick that you anchor to the splash pan with a wad of clay. Throw your first mug, then set up the gauge to point at the rim of the fresh pot before you cut it off the wheel. Throw the subsequent mugs so that the rims match. If they're all the same height, the rims are the same width and the form is otherwise pretty close, they'll all read as a set.

Making your first plaster mold will take waaaaay longer, and be far more frustrating and messy. And that's not even dealing with deflocculating your slip properly, or figuring out the right amount of time for the slip to be in the mold, especially with back-to-back castings. Or potential warpage if the resulting mug gets taken out of the mold wrong.

 

Trust the skills you already have.

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Just smiling re. posts about moulds and molds, not about to say anything but misuse has occurred in 2 posts

ANd another post has discolouration which may in fact be mould from the mold . MuY advise is to wash the mugs, not just the insides..

May be better time wise to just throw a lot of mugs and pick out the most similar, if the client is after identical..but chose you to make mugs, can't see the client's reasoning other than she likes your work so go throw mugs and let him select from a few... may not want them identical

 

Did anyone misuse the mould/mold word? I've always though that "mold" is used in the US and "mould" used everywhere else and both words mean the form(ing) of an object, the growth of the black stuff and moulding trim. Maybe the spelling has changed over the years?

 

 

That is my understanding as well. Mold/mould, color/colour, theater/theatre, etc.

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Mold vs. mould

American English has no mould, and British English has no mold. In other words, the word referring to (1) the various funguses that grow on organic matter or (2) a frame for shaping something is spelled the same in both uses, and the spelling depends on the variety of English.

Of course, the spelling difference extends to derivatives such as moldy/mouldy and molding/moldingand to the verb sense to shape with a mold. 

Australian and Canadian English favor the British spelling, though mold is fairly common in Canadian publications.

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Mold vs. mould

American English has no mould, and British English has no mold. In other words, the word referring to (1) the various funguses that grow on organic matter or (2) a frame for shaping something is spelled the same in both uses, and the spelling depends on the variety of English.

Of course, the spelling difference extends to derivatives such as moldy/mouldy and molding/moldingand to the verb sense to shape with a mold. 

Australian and Canadian English favor the British spelling, though mold is fairly common in Canadian publications.

 

Wiki? Neil? Show your bibliographies please.Now I was born/borne back in the dark mouldy past of the British Isles.

I was caned into spelling correctly....definitely was two spellings and two meanings then. But my teacher was from a faraway place ..England I think

Any erors in my spelling now are typos!!!!!

I think mold is actually a town in NE of Wales

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Sorry Babs, the only mold in English is in Wales.

 

I looked in 1968 and 1979 dictionaries and mold doesn't appear at all.  It does in 1995 dictionary, but with [uS] after it.

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Sorry all for the diversion.

I hope OP AndreaB is busily making lots of mugs on the wheel and that she gets a great response from her client.

 

That I am. They are however evolving into a different form. Not a bad thing in itself, people always like mugs and my hubby wants mugs for his studio.

 

I took a video of the throwing and sent it to my client and she was amazed at the whole process, so I think she'll be more appreciative of the final result.

 

This one was made especially for him

 

post-65376-0-17240300-1461388623_thumb.jpg

post-65376-0-17240300-1461388623_thumb.jpg

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Sorry all for the diversion.

I hope OP AndreaB is busily making lots of mugs on the wheel and that she gets a great response from her client.

 

That I am. They are however evolving into a different form. Not a bad thing in itself, people always like mugs and my hubby wants mugs for his studio.

 

I took a video of the throwing and sent it to my client and she was amazed at the whole process, so I think she'll be more appreciative of the final result.

 

This one was made especially for him

 

attachicon.gif13002348_1133171843371534_8428539728330838012_o.jpg

 

 

 

Andrea, just to put my two cents in: I've both used and made plaster molds and I'd like to suggest that it will take you far less time and effort to make a dozen or even 18 mugs and choose the four closest in size and shape as the set for this customer rather than deal with the learning curve not only for mold making but for learning to slip cast, all for four mugs. This will give you lots of valuable practice and also you will have quite a few other items to sell when you're done. 

 

I know that slip casting is perceived as so "easy" that it seems to be looked down upon by those who make "real pottery". For myself and anybody I've ever talked to who has done slip casting and mold making, we have all agreed that wheel throwing (once you've got past the learning phase) is much easier and faster, though of course you don't get the identical results. I'm okay with that because I want my things to be obviously handmade. 

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Joel:

There is a difference in urban and rural slang, north vs. south, and east vs. west. Around here, defence is the removal of rusty barbed wire, or a few slates the cows knocked down. Up around Washington D>C, defense is roughly 1/3rd of the budget and screwdrivers cost $100 each: or $200 if a double shot is used. We use all natural defense around my house: a skunk sleeps under the chair on the front porch: ring the doorbell and he will spray your.. nevermind.   Burrow=donkey=or a**.

Nerd

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Hi everyone,

 

Thanks for all your comments and advise. They are really much appreciated.

I would just like to explain a little on my thought process with this. 

 

I'd throw a template that I liked. Then make a mould/mold and use this for future items. The second thing I had in mind was that I've just purchased a 3l of porcelain slip and wanted to try casting with it., and also some other stuff.

 

It seems that I have a knack for posting questions that evolve into a much discussed topic and debate. A great thing for a forum.

 

I need to get onto making handles and attaching - not one of my strong points at the moment, but practice make perfect!! :)

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OK, some very basic steps to make a two-piece mould, assuming your mug is symmetrical and has no undercuts and is flat footed:

 

  1. Make a sample mug that you like.  Keep it leather hard.
  2. Lay mug on it's side supported by "old/scrap" clay.
  3. Put scrap clay up to half-way up the sides, make sure it is level and flat.
  4. Put a plug of scrap clay inside mug, extending 2inches beyond rim.  (Inside and not covering top of rim.)
  5. Build walls around clay and mug, varnished plywood is good.  Wood should be at least 2inches taller than height of laying down mug, and 2inches further from mug all round.
  6. Secure wooden walls with clamps or straps.  Plaster is strong and heavy and it will escape if you let it.
  7. Seal corners inside or out whichever is easiest with scrap clay.
  8. Apply three coats of soapy release onto wood, allowing to dry between coats.
  9. Calculate volume of plaster required - w*h*d/10 in centimetres gives volume in litres ( 30cm x 30cm x 5cm  = 4,500 or .45 of a litre.  (12" x 12" by 2")
  10. Mix plaster using amounts as per photo below.  (Water in bucket first, then sprinkle plaster, wait 2 minutes, stir gently for 2 minutes - stir with rubber-gloved hand, making sure no lumps.)
  11. Pour plaster into box.  Lift baseboard up and drop gently a couple of times to bring air-bubbles to surface.
  12. Leave 1 hour.  Remove boards and clean up.
  13. Remove scrap clay, but leave rim plug in place.
  14. Turn plaster block and original mug over so plaster is now on the bottom.
  15. Twist coin or similar into plaster in two places on each side of mug, making an inverted dome.  This will keep the two halves of the finished mould located.
  16. Build walls up around as step 5.  
  17. Repeat steps 6 to 12.
  18. Use a rasp to remove sharp corners on outsides of plaster.
  19. Leave to dry out for several days.
  20. Remove plug and original mug.
  21. Clean soap from plaster with vinegar.
  22. Put rubber bands or strap around and leave to dry for several days.  Moving air is better than heat.
  23. Pour liquid slip, leave until desired thickness, pour slip out, leave to drain.
  24. Leave to set-up/until leather-hard.
  25. Remove from mould, fettle, fire..........

Enjoy

 

gallery_59202_1063_8433.png

 

 

I'm sure the rest of the gang will chime in if I've missed any important steps, but it is worth spending time to read up about mould-making - best book I've come across is this one:  https://www.amazon.co.uk/Essential-Guide-Making-Casting-Ceramics/dp/1600590772

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Sorry all for the diversion.

I hope OP AndreaB is busily making lots of mugs on the wheel and that she gets a great response from her client.

 

 

That I am. They are however evolving into a different form. Not a bad thing in itself, people always like mugs and my hubby wants mugs for his studio.

 

I took a video of the throwing and sent it to my client and she was amazed at the whole process, so I think she'll be more appreciative of the final result.

 

This one was made especially for him

 

attachicon.gif13002348_1133171843371534_8428539728330838012_o.jpg

I think making the video for your client is brilliant!

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