[Clayart] durable outdoor planters

[vpitelka at dtccom.net]

Hi Sumi - 
Do you know if this information is from Val Cushing?  I am sure other people have come up with good information about claybodies to survive hard freeze, but I am curious where you got this info.  If it is reliable info, I'll save it for future reference, especially if it is from Val Cushing.  
Thanks - 
- Vince

Vince Pitelka
Potter, Writer, Teacher
Chapel Hill, NC
vpitelka at dtccom.net
www.vincepitelka.com 
https://chathamartistsguild.org/ 

-----Original Message-----
From: Clayart <clayart-bounces at lists.clayartworld.com> On Behalf Of sumi
Sent: Wednesday, May 11, 2022 4:28 PM
To: clayart at lists.clayartworld.com
Subject: Re: [Clayart] durable outdoor planters

Phyllis

Many potters will say you want a clay body with as little absorbency as possible. However, what I've been reading is that you want a clay body with the correct saturation coefficient. This is calculated by weighing a dry, fired test tile, then soaking it in water for 24 hours, then drying and weighing again. Then, boil them for 5 hours, dry them off, and weigh again.

Divide the soaked absorption rate by the boiled absorption rate to get the saturation coefficient.

SO:

(Soaked weight - dry weight) divided by dry weight = soaked absorption rate

(Boiled weight - dry weight) divided by dry weight = boiled absorption rate

Soaked absorption rate divided by boiled absorption rate = saturation coefficient.

If your clay absorbs 3% when soaked and 4% when boiled, your saturation coefficient is .75

Saturation coefficient should be less than .78

I've seen sources state it should be less than .78, some say "about .78"

Not sure which is correct.

Sumi
>   I have made several planters over the course of my pottery passion. 
> Some of them hold up to the winter (occasional freezing temperatures), 
> and some don't. I would love to be able to pinpoint what I am doing 
> both right and wrong because I would like to make some larger sized 
> planters. But of course I want them to be able to withstand the 
> occasional freezing temperatures that we get in Virginia. Does anyone 
> have any suggestions or tips for making these pots? I do both 
> handbuilding and throwing but I will probably make these planters from 
> extruded coils. As always, thank you in advance for your help.
> Phyllis Canupp
> -------------- next part -------------- An HTML attachment was 
> scrubbed...
> URL: 
> <https://lists.clayartworld.com/pipermail/clayart/attachments/20220511
> /8340b7a2/attachment.htm>