Slip Casting Handles

[hitchmss]

Hey Gang, long time no talk....too busy making pots to get on here and throw my $.2 around even though Id like to!

I searched in the back pages to see if this was covered somewhere else, but couldnt find the answer to my question, but if it already has, please advise and/or delete.

I make about 1,000-1500 pots a year for which I also make (aside from extruding) handles for these said pots. I pull handles for mugs, and throw knobs/handles for some bakers. While Im efficient at the process, it still adds up to a bunch of time just in making the handles, and Id like to find a more consistent/expedient process for doing this, so I thought Id research into slip casting them.

Making the molds is not my issue; plenty of experience making molds and using numerous different materials (silicones/urethanes/gypsums/etc). My question mainly lies in the casting slip. Having very little (all intensive purposes, consider it zero) experience with slip casting, my knowledge of said materials makes me think that a deflocculated slip cast handle is going to shrink a lot less than my throwing clay body (Bmix ^10), and this will obviously be an issue.

Can I cast with a non deflocculated slip? Ideally Id love to just add some suspension agents to my slip and pour away. Will I have issues doing this with my castings?

Obviously, the higher water content will lead to saturated molds much faster, which Id just offset with more gang molds-no biggie. Im also hoping that this will benefit me some; my pulled handles are thicker at the top, thinner at the bottom. If I pour these molds with the thick/top up, and thin/down, I would think there would be a higher concentration of water in the bottom portion of the mold (gravity), and thus, hopefully my handle bottoms wont be much drier than the tops upon removal from the mold.

Id need the handles to come out of the molds soft enough to still bend into shape to attach (Not sure that I want to make molds of handles in a "pre-bent" shape), so Im thinking I will have some challenges with timing the extraction of these castings, but with experience....If they do need to come out too firm to bend, I could always rehydrate, which is time, but not a huge amount of effort.

Anyone have experience with this? Anything Im missing? Dont want to spend a lot of time/money on this to find out that its a complete waste.

Thanks in advance!

[Mark C.]

I never had any luck with bending slip wares-they do not like it

I think the extruded handle is your best option (its what I do with thousands of handles per year)

slip ware just does not bend well as it cracks . The way the particles line up is my thought as they tear easy with bends.-Your extruded handles will be 25 times stronger with all the compression.

[Hulk]

Interesting!
I enjoy pulling handles and will very likely keep plodding along with it for ...ever.

Seems that extrusion is the common alternative, however, handling would be required to get the taper.
I've been curious if stamping out handles could be an alternative?

[hitchmss]

10 minutes ago, Mark C. said:

I never had any luck with bending slip wares-they do not like it

I think the extruded handle is your best option (its what I do with thousands of handles per year)

slip ware just does not bend well as it cracks . The way the particles line up is my thought as they tear easy with bends.-Your extruded handles will be 25 times stronger with all the compression.

I extrude a boatload of handles for other pots. They look "ok", and are quick, but for some things I just want that pulled handle look.

I was wondering about the particles/strength of the cast handles. Not having any experience, I wasnt sure. Similarly, wasnt sure if a defloc vs non defloc slip would be stronger/weaker in this regard.

 

[hitchmss]

9 minutes ago, Hulk said:

Interesting!
I enjoy pulling handles and will very likely keep plodding along with it for ...ever.

Seems that extrusion is the common alternative, however, handling would be required to get the taper.
I've been curious if stamping out handles could be an alternative?

I worked in a tile studio and we press molded a lot of tiles. I hadnt thought about press molds to be honest.... This might be a better alternative to slip casting.

I enjoy pulling a few handles, but I make about 500 mugs a year which I pull handles for, and it takes me about 5-6 mins per handle to pull which equates to about 42-50 hours a year just in pulling handles.

[Chilly]

As @Mark C.says.

Slip cast handles are hard to make so they are solid.  Mine always ended up with a hollow down the centre.  No amount of re-topping the reservoir, changing the viscosity etc,  made any difference.  As soon as I put any pressure on the handle to change it's shape it squashed or flattened.

[hitchmss]

15 minutes ago, Chilly said:

As @Mark C.says.

Slip cast handles are hard to make so they are solid.  Mine always ended up with a hollow down the centre.  No amount of re-topping the reservoir, changing the viscosity etc,  made any difference.  As soon as I put any pressure on the handle to change it's shape it squashed or flattened.

i assume this was using a defloc slip? I wonder if a non defloc slip, being higher in water content, would take longer to gel/set, and thus might give fill solid? When you let your castings dry after filling the molds, were they vertical, or on a slight angle? I wonder if an angle might increase the chances of casting solid? Maybe setting the molds onto a vibrating table as they set? Not sure if any of these have merit, just brainstorming. Would love to find a way to make this work, but again, time/money invested only to fail....

[PeterH]

a sprig mould?

[Mark C.]

We do a fair amount of press mold handles on baking dishes (they are shell shaped ) and they get 90 degree bend-so press mold is a yes if that helps

They are from the same porcelain mix as the slab dishes are made from 3/4 porcealin and 1/4 wso

some are 100% porcelain  as well (the smaller dishes)

On handles I handled 60 mugs yesterday in about 1 hour 45 minutes (taking my time includes extruding) these where 1# mugs -

today it  will be 50 more mugs 30 are 1.5# mugs the other 20 are 1# mugs-the larger handles take more time.

all mugs have a thumb spot so that takes a bit more time.

[oldlady]

extruded blanks can be tapered by rolling, takes only a few seconds.  add interest by pressing into a mold shown above by Peter or use some rubber floor mat like The Pottery Boys  show on their website.  one roll with a pony roller produces the "ribs" in the handle.  can"t link you but they show exactly how to do it.  hardware stores sell the mat by the yard.

[Chilly]

6 hours ago, hitchmss said:

non defloc slip, being higher in water content, would take longer to gel/set, and thus might give fill solid? When you let your castings dry after filling the molds, were they vertical, or on a slight angle? I wonder if an angle might increase the chances of casting solid?

I tried all variations of angles, and more water/less water

 

6 hours ago, hitchmss said:

vibrating table

but not this

 

Rolled handles and a template to dry them on in the required curve was the best I got to.  Then stopped making mugs.

[PeterH]

4 hours ago, oldlady said:

...
The Pottery Boys  show on their website.  one roll with a pony roller produces the "ribs" in the handle.  can"t link you but they show exactly how to do it.  hardware stores sell the mat by the yard.

Different methods of making handles for mugs https://tinyurl.com/yckrtf6r
Video: https://tinyurl.com/mrnwfa5b

[Denice]

One of my college assignments was to make a dozen nice mugs for a Valentines sale to  raise money for a NCECA  trip.  I was in a hand building class so I made mugs that look like hearts on top and butts in the from.   They needed a very stylized handle,  after I made a few,  I realized that it was taking too long.   So I made a press mold of several handles and was able to finish on time.  I still get request for butt mugs,  I am glad I kept the handle press mold.   Denice

[Bam2015]

I personally use a Scott's Creek handheld extruder for handles. I dislike pulling handles and extrusion is quick and reproducible.  I believe that Shimpo has a similar version and maybe there are others as well.

Betty

[oldlady]

thanks, peter, floor mats make wonderful leaves, too.  back them with duct tape to make a handle so you can press leaves into clay easily.  i do have a hard time turning the mat so i do not cut two of them going the same way.

[PeterH]

On 2/9/2022 at 4:22 PM, hitchmss said:

Can I cast with a non deflocculated slip? Ideally Id love to just add some suspension agents to my slip and pour away. Will I have issues doing this with my castings?

I don't think anybody has directly addressed this question.

Understanding the Deflocculation Process in Slip Casting https://tinyurl.com/2p96x33r

A simple mix of clay and water will not work well at all for casting. Not only will it quickly waterlog the molds but it will shrink too much (and therefore crack in the molds) and it will take much to long to cast. It will also gel and settle out and generally make the process miserable. Optimal casting requires that the slurry have minimal water content (e.g. 30% instead of 60%), good flow and draining properties and that it not settle out or gel too quickly. When the slurry is right the casting process works amazingly well.

... I suspect that these issues are amplified if you are trying to solid-cast.

[hitchmss]

17 hours ago, PeterH said:

I don't think anybody has directly addressed this question.

Understanding the Deflocculation Process in Slip Casting https://tinyurl.com/2p96x33r

A simple mix of clay and water will not work well at all for casting. Not only will it quickly waterlog the molds but it will shrink too much (and therefore crack in the molds) and it will take much to long to cast. It will also gel and settle out and generally make the process miserable. Optimal casting requires that the slurry have minimal water content (e.g. 30% instead of 60%), good flow and draining properties and that it not settle out or gel too quickly. When the slurry is right the casting process works amazingly well.

... I suspect that these issues are amplified if you are trying to solid-cast.

Thanks for answering that Peter! I had always heard to cast using a defloc slip as the particles would evenly disperse (as well as lower water content), but wondered if being cast solid would provide different results. It seems based on a lot of good advice that slip casting these handles wont work, so Im going to pursue press molding these instead. Thankfully, Ive got enough experience with making/using press molds that this should be a relatively painless journey.

[Pres]

Since my thumb surgery, I can no longer pull handles right handed, and am too awkward with my left hand. The power extruder gives me plenty of pressure to create well made handles that fit my mugs well. I do add a bit of stretch by slamming on flat surface diagonally to thin the bottom of the handle slightly. adding lugs in the bottom and thumb pressed balls in the top finishes the job. I have tried nearly every technique under the sun to make handles that look good, feel good, and hold up well. . . . extruding fits the bill the best.

 

best,

Pres 

[LeeU]

On 2/10/2022 at 5:33 PM, Bam2015 said:

Scott's Creek handheld extruder for handles

Would you please describe a ball-park idea of how much forearm strength and grip pressure is needed to use the handheld extruder? I can squeeze my hand slowly/repeatedly and hold firm but not much more than it takes to work a tough handheld pressure kitchen tool, like a heavy duty manual can opener or tight/heavy garlic press. THX

[Chilly]

I use an extruder, horizontally, next to a corner wall.  Use the side wall to push the handle in.  I tried it upside down, pushing handle on floor, but that was not good.  Also tried right way up, pushing handle up against greenhouse  bench, but that lifted the bench !

Similar to this. 

[oldlady]

lee, i tried a hand held extruder and found that i could not make the entire extrusion  long enough for a handle.  each pull creates a stop where you need to start squeezing again.   who is it here who made one from an electric caulking gun.   is it pres?   that might be a way for you as well.

[PeterH]

40 minutes ago, oldlady said:

lee, i tried a hand held extruder and found that i could not make the entire extrusion  long enough for a handle.  each pull creates a stop where you need to start squeezing again.   who is it here who made one from an electric caulking gun.   is it pres?   that might be a way for you as well.

Two page article (as jpegs) by Preston Rice & Madeleine Coomey  ?
https://1.bp.blogspot.com/-xYr-ZLHHRyc/XGsvzDufnKI/AAAAAAAAA0U/zISVLs-TKzQ3RPNKwFoc2rZ4CNnpzi3iQCLcBGAs/s1600/TT_RiceCoomey.jpg

https://4.bp.blogspot.com/-6bczNxLZFgI/XGswHUKVTOI/AAAAAAAAA0c/K5DZtUz323YGyY0UNfsVDQCP0k-LhPtRgCLcBGAs/s1600/TT_RiceCoomey2.jpg

From https://picworkspottery.blogspot.com/ (Pres's site?)

 

Also as Tips and Tools: Extruder Conversion  https://tinyurl.com/47cbbuv9

Edited February 14, 2022 by PeterH

[Bam2015]

Lee, see my private message to you. I didn't want my response to get lost in this post. 

Betty

[oldlady]

peter, you are remarkable!   thank you again.

[PeterH]

@liambesaw You seem to be joining plastic handles to slip-cast pieces. Any comments for this thread?