Jump to content

Hump molds

Recommended Posts

I'm liking the hump mold approach because I can basically finish the pot in one go except for adding a rim.  I can attach feet and whatever applied textures.  My thinking is that working with wet clay will give me the best chance for flawless joints.  The problem with hump molds is that the clay shrinks, grabbing the mold more tightly.  The wet clay can't be removed from the mold wet if there is any adhesion to the mold without distorting the pot.  My solution is to cover the mold with plastic wrap from the kitchen.  You know, the super clingy stuff.  It's really thin and doesn't add any texture to the inside of the pot even if there are folds.  2 or 3 pieces will cover the hump mold and then the slab is worked down.  Pot lifts right off wet or leather hard. 

Link to comment
Share on other sites

Slump molds are easier to use as you can walk away from them and the clay shrinks away and does not crack-I can see why you like hump molds as you are working on the outside surface more than the inside.

I try to put all texture or whatever on the slump mold and avoid all hump molds -just is easier to to monitor as much after clay is in them.

It depends on what you ae wanting to do witgh inner or outer surfaces

Link to comment
Share on other sites

  • 1 month later...

My only problem is that the finished hump mold is too heavy.  At 19 x 12 x 6 it's actually only about an inch or so of hydracal as a shell, hollow, but it still weighs 17.5 lbs.  With 10-15 lbs of clay, it's uncomfortably heavy to flip over on the bat.  My consultant (next door neighbor is a sculptor) suggests pour able foam.  It's like the stuff that comes in the can for sealing window cracks from Home Depot.  That stuff could work also, but there are denser materials available from Pour On.  I don't want the open cell nature I've seen with the canned stuff.   I'll just have to remake the slump mold off my current mold and then pour the new one in foam.  Kind of expensive, around $100 in materials.  Could be worth it.  Needs more research.

Link to comment
Share on other sites

I also like slump molds, using a wooden frame with a piece of fabric pinned at four corners. Works well, and size is never an issue.

However, there are times that I have made hump mold from student using a sheet of 2" thick styrofoam insulation, cut to shape, then another contact cemented to that one, until I got the desired rough shape. Use a surform tool to compete the shaping then form away. These last a long time and will work well.






Link to comment
Share on other sites

On 2/22/2020 at 4:15 PM, CactusPots said:

I got a couple of oval mold patterns from Pure and Simple for making plaster slump/hump molds.  Neither was exactly what I wanted, good size, but not deep enough.  One I added a big slab of set plaster and just surformed it to shape and the other I only wanted a little, so I just set it on a formed to shape piece of plywood.  So far so good.

Not being content, I want a max sized oval for my kiln, so 19x12 or so.  I looking at how to create the master.  The only ideas I have come up with so far are multi stack plywood, cutting each oval smaller from the top down and then hogging off material to get the final shape.  I can do this as I have a bandsaw and other wood working tools.  The trick will getting it laid out correctly on paper. 

The other idea I'm kicking around is thick styrofoam and a heat knife.  I've even seen some advertised with bendable blades.  Maybe I could get a 6" thick piece of styrofoam cut the way I want it in one pass.  No experience with this so totally speculation.

Other than finding the perfect bowl and just pouring the plaster, any other ideas on how to make a symmetrical, oval hump mold to my specs?

Bill van guilder has a free video on YouTube or his website on how to make a hump mold. Very simple 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...

Important Information

By using this site, you agree to our Terms of Use.