Lowell Hill Pottery

Continuing the Rowantrees Tradition

207-951-8229

  • Home
  • About LHP
  • Shop
    • Ordering Information
      • Downloadable Price List
      • Terms and Conditions
      • Return Policy
      • Your Privacy and Lowell Hill Pottery
    • Lowell Hill Glaze Colors and Patterns
    • Lowell Hill Exclusives
    • Tableware
      • Plates
      • Bowls
      • Cups and Saucers
      • Mugs
    • Beverage Servers
    • Food Service Items
    • Ovenware
    • Accessories
      • Ornaments
    • Condiment Servers
    • Sets
    • Gift Suggestions
    • Welcome to the Gift Registry!
      • Metcalf/Lien
  • Wholesale
    • Terms
    • Registration
    • Wholesale Login
    • Download Catalog
    • Ordering
  • Contact Me
You are here: Home / Archives for Blog

About Your Old Rowantrees Pottery UPDATED

Posted on07.01.18 by Geoff Miller

I often get questions in email from folks who have older sets of Rowantrees pottery. A few years ago, most of them centered on the current value (sentimental, quite a lot; monetary, not so much). Others were curious about pottery they had picked up at yard sales or auctions – mostly asking about when a piece was made or by whom (hard to say for certain, but a few minutes of research can provide clues). But two other questions still come up from time to time; durability and food safety.

The short answer to both questions is, “It depends.” I will give the longer answers here and in the order listed above.

The issue of durability generally extends to everyday usage, microwave-ability, and dishwasher safety. How well any pottery will hold up depends on how it is used and how old it is. Nothing lasts forever, and potters do all they can to be sure their products will last as long as possible. I have seen sets of Rowantrees pottery that were decades old and still looked like new. I have also had Rowantrees less than ten years old fall apart in my hands. Rowantrees is earthenware, which is the least durable type of pottery. That doesn’t mean it won’t last a very long time, but you see far fewer pieces of earthenware in museums than you do porcelain (the most durable type of ceramic ware). The big difference is firing temperature and the type of clay used. I can go into more detail on this in another blog post. For now, a simple answer to the question of durability is in order.

Durability

Rowantrees was made for everyday use and it would seem most people used it that way. Modern dishwashers and microwave ovens did not exist for some time after Rowantrees was founded, but it did seem to hold up well in both. That said, it tends to heat up in the microwave, so care should be taken when removing dishes after heating (the same goes for Lowell Hill Pottery). Further, food should cover most, if not all, of the bottom surface of the dish to avoid uneven heating, which can cause cracking.

Dishwashers present a challenge for not only handmade pottery, but for all breakable dinnerware. The issue is not the water temperature or the alkaline detergents used, but rather the force of the water jets that can cause dishes to rattle about and bang into each other. Careful stacking can help with this issue, but most dishwashers are built to handle a wide variety of ware thicknesses and to allow sufficient room for water and soap to get in and do their job. More often than not, flats like plates cannot be stacked snugly enough to prevent moving about.

Rattling about in the dishwasher will reduce the life of most pottery. It will still last a good long time, but something thought to last up to fifty years may limp across the finish line after only twenty or thirty.  So how long your pottery will last depends on a lot of variables. I doubt it’s the same length of time from one home to another.

Food Safety – an Undefined Term

There is no standard definition for “food safety”, which makes a determination very difficult. In general it is better to look at the toxicity of the materials that went into making the pottery and then determine if those toxins remain stable in the glaze or leach into food. Then the degree of leaching has to be determined to see if the results exceed safe levels.

Don’t get me started on those safe levels. In most cases, they haven’t even been determined. Even when safe levels have been determined, they change frequently as new research shows that we were wrong – again. The best course of action for any potter is to use as few toxic materials as possible in manufacturing their wares.

Just remember, in sufficient quantity, both water and oxygen are toxic.

Rowantrees pottery was made using lead. There, I said it. Most people are aware of this and I get frequent questions asking about its safety. My liability insurance provider would look askance at me making declarative statements of perfect safety, so I won’t do that. There are, again, too many variables. But I will tell you this; to the best of my knowledge, there has never been a case of lead poisoning caused by the use of domestically produced ceramic ware. The incidents involving lead glazed ware causing toxicity involved wares produced in other countries and imported to the USA. And in these cases, the lead leached into food (usually beverages) that was a) acidic (lemonade, tea, orange juice, etc.) and b) stored in the pottery vessels for over twenty-four hours. Since most people put food into their pottery and then consume it in a relatively short period of time, there is no opportunity for lead to leach into the food.

Rowantrees went through a regulatory ringer in 1986 over its use of lead. At that time, the issue was less about food safety than it was workplace safety, but the glazes got tested. Pieces were soaked in acetic acid for twelve to twenty-four hours and then the acid was tested for lead content. While all glazes had passed testing a number of years earlier, the standards had changed and several of the glazes were found to leach excessive amounts of lead. When Rowantrees sought out an independent laboratory to test the glazes, they discovered that this release occurred only on the first time around, and that subsequent tests showed little to no release. The conclusion that Rowantrees drew from this was that the initial high lead levels in the acid were not due to lead leaching from the glaze but from lead fuming that settled on the pottery in the final stages of firing. From that time on, Rowantrees soaked all pottery coming out of the kiln in a vinegar bath for at least twelve hours then washed each item before putting wares on the shelf for sale.

So I don’t consider lead to be an issue with Rowantrees. Lowell Hill Pottery does not use lead due to the aforementioned workplace safety issues and because lead has become such a hot button issue it’s best to stay away from it.

A much bigger concern for food safety is the condition of the pottery itself. Look closely at your pottery. Is it chipped or cracked? Can you see a network of fine crackles on the surface? Has the glaze flaked off anywhere (particularly on the rim)? All of these issues can spell a food safety problem. Pottery that is cracked or crazed (that network of tiny crackles) is inherently weakened. Cracked pots can break when stressed by heat. Try putting hot pasta on a plate with a crack in it. You might get away with it once or twice, but sooner or later you will hear a loud snap and your plate will cleave in two. Chips on the rim leave areas of unglazed clay that will absorb moisture, weakening the pottery. Worse, bald spots on the food contact area can absorb pathogens that will not be destroyed by high water temperatures. Crackles (crazing) can often lead to both moisture absorption and a foothold for pathogens. You can still use the pottery, but I wouldn’t store raw meat on it.

So there it is; a brief (yes, this is brief for me) overview covering issues raised most frequently. I am almost certain that I have left some questions unanswered, so please don’t hesitate to contact me if I have not addressed a concern you have. I will update this blog with any information I can.

UPDATE: Since I published this post I have been made aware of a study done to determine whether or not crazing on pottery surfaces increases the risk of pathogenic illness. The study found that pathogens were easily eradicated on pottery washed in a dishwasher, while dishes washed by hand were somewhat more problematic. Dishwashers typically use water heated to sanitizing temperatures that are far too hot for handwashing. In addition, most dishwashers exchange water between segments of a cycle, while people washing dishes by hand tend not to change water more than once, if at all depending on load size. Most importantly, the results were the same whether or not crazing was present. So it would seem that crazing on pottery surfaces has less to do with potential exposure to pathogens than the manner in which dishes are washed.

The New Shop Takes Shape

Posted on12.30.16 by Geoff Miller

Wall Framing Day 1

Ground preparation started in early July. Despite a rainy day and a holiday, the work of getting everything ready for the construction crew took only three days.
Day 1

day3

day94The gravel work finished, it was a month before the cement slab could be poured. Contractors are busy people in the summer. But finally it happened. Done in just two days.

Forms Forms 2SlabThe cement was allowed to set for about three days – the warm weather making the short time period possible – and then the framing supplies began to appear. Most of the lumber and the trusses arrived followed shortly by doors, windows and other supplies. The construction crew was delayed by a rainy day, but got underway quickly as soon as they were able.

The framing went up in two days.

Framing Day 1Wall Framing Day 1Note the headers on this wall. If I had just built a “shop” beside my house, it would have added no real value to my property. By adding these headers, I made it possible for some future owner to convert this building into a two-car garage. I can’t even imaging when anyone will want to do that (I certainly don’t plan on going anywhere soon), but the fact that it can be done adds value.

Finished Wall FramingThe roof (or most of it) was framed the next day. It’s a simple truss roof given that future plans are to remove the roof and add a gambrel roof to create a second story (I’m not giving up on that idea).

Roof TrussesActually, this picture was taken around lunch time. But the end of the day a lot more had happened:

Sheathing 1Sheathing 2Finally, it was time for the roofing, doors and windows.

New StudioTotal building time (after the cement pad): 5 days.

Thus ended the first chapter of the New Studio Build. The outside is easy and goes up fast. the real time consuming work happens on the inside. I’ll be writing on that soon. For now, here are a couple pictures of the inside of the shell.

Inside 1

 

Glazes Part 2 – Many (Overwhelming) Choices

Posted on09.22.16 by Geoff Miller

Chalices

Chalices

Potters face a bewildering set of choices when creating and using glazes.

There are many different surface treatments for pottery and ceramic sculpture, but glazes are by far the most popular and common. Glazes can be shiny, matte, stony, cratered, crackled, glassy smooth, crystalline, and textured in a number of ways. They can be colored in almost any color that can be perceived by the human eye. These variations can be created, effected and affected by formula, method of application (brushing, dipping, spraying, splattering), thickness of coating, the firing schedule and type of fuel used for the kiln.

If all of this leaves you overwhelmed, add in the multitude of choices when it comes to raw materials for creating glazes and it’s easy to see why so many potters choose to use commercially produced products. These tend to be very stable formulations that behave predictably when used as suggested. Many potters use only a couple of base glaze recipes and alter them with different colorants or by changing the ratio of silica to alumina to adjust the gloss or matte of the glaze. I follow that philosophy when creating new glazes. But even that method has its limits. Here is a tale of my own experience.

I needed a new green glaze that was unrelated to the Rowantrees reproduction Evergreen that I already sell. This new glaze needed to have an “antique” character to it, with the green more muted and not as bright. I already had a good, stable recipe for a clear glaze that I had used to make a similarly antique white, blue and yellow. So I decided to try that recipe to make green. Reasonable, no?

Well, no, it wasn’t. Green is usually made by using either copper or chrome. Copper creates a reliable green only in lead-based glazes and in some high-fired glazes. Because all of my glazes are fluxed with boron – and I fire in the medium temperature range – copper created turquoise to blue. So copper was out for making green. That left two choices for me. Either I could use a green stain (more on that later) or chrome. Chrome was the less expensive choice and I already use it for the Evergreen, so I had a supply of it. I only need about 1% chrome to make a strong green color, which is very little as well.

Here’s the thing; every time I made a test batch of my base glaze using chrome to make green, the best I could manage was olive drab. Mind you, it was a pretty glaze that I intend to explore (particularly in combination with other colors), but it wasn’t what I was trying to achieve. Nor was it what my customer was waiting for.

What was going on here? Well, a little research told the story. The base glaze contains both lithium and zinc. Lithium is an alkaline metal and exists at the “reactive” end of the periodic table. In fact, lithium is possibly the most reactive after hydrogen. Zinc and chrome are transitional metals, with chrome being more reactive. When chrome is added to a glaze containing either lithium or zinc the result will tend to brown. So there you have it. I needed a totally new glaze recipe.

Nobody likes coming to that conclusion, but there you have it. I chose to adapt the turquoise recipe, which contains neither of the troublesome fluxes and got a satisfactory green. Sometimes the answer is right in plain sight.

Next time: common glaze defects to watch out for.

The Studio Saga – Good News!

Posted on05.15.16 by Geoff Miller

Studio

Studio

Finally! Although a date has not yet been set for the start of construction, the new studio will be built this season. It was a struggle to get to this point, and plans had to change (don’t they always?), but the home stretch is finally upon us.

You may recall in earlier posts that I had said I would do whatever it takes to just get a roof over my operation so I can have a work space and a place to sell my pottery. I’m at that point now. About a week and a half ago I spoke with the contractor. The next day I had a new estimate from him. Thanks to the gracious assistance of a deer tick I had to take a couple of days to see to my health, but the following Monday I sat down and plugged the new numbers into the cash flow spreadsheet.

No negative numbers. We’re in business again!

So the new studio as planned now is a 24′ by 36′ two-car garage style building with two doors and two windows. It will have no insulation or heat. Nor will it have a second story – at least for now. And it will have a simple gable roof rather than the gambrel originally intended. I will operate seasonally as I have up to this point, and will add insulation and drywall as I am able to. When the building is insulated and the drywall finished, I will then consider a heating system (I already know what I want) and will move to year-round operation. I’m not sure how long this process will take. How well business develops will certainly play a role.

This is a realistic plan that will get me up and running.

The best news in all of this is that the bank is on board. They like  the business plan and feel my numbers are realistic. Best of all, they believe in me.

The new studio will happen this year. It’s more modest than first envisioned, but it will work. Keep an eye out here for updates. They should start coming our more quickly soon!

Answering Your Questions – Glazes Part 1

Posted on01.30.16 by Geoff Miller

Mugs

I often get questions about pottery glazes: exactly what are they, what are they made of, are they safe, how long should they last, and quite a few others. In this and several coming articles, I will be discussing these questions. The more you know about pottery and glazes, the better informed your purchasing decision will be and the happier you will be as a result.

So to the first question: What exactly are glazes?

In the simplest terms, glazes are suspensions of minerals and metallic oxides that are used to coat ceramic forms. When applied to those forms, the water soaks into the clay form leaving an even coating of the minerals and other materials on the surface. When fired to the correct temperature, the glaze materials melt to form a glass coating on the form.

Sounds pretty simple, right? Tomes have been written on glazes. New recipes are created every day. The vast majority of these are discarded as failures. Only a few of those that succeed will see regular use. Even fewer will become favorites destined to be used for many, many years. A fraction of a percent of them will become heirloom glazes recognized throughout history and in many cultures. The art and subtle science of glaze making are complicated, and as time goes on, the preference for mere beauty is equaled by a need to safety and permanence.

But enough marketing talk, what are they made of?

At its simplest, a glaze contains three things; a flux to promote melting, a glass maker to form glass and an intermediary to harden and stabilize the glaze. The most common fluxes are sodium, potassium, boron, calcium, magnesium, lithium, zinc, barium, strontium and lead (pretty much in that order). Each of these has its own specific set of properties and behaviors; advantages and disadvantages that need to be kept in mind. Usually a glaze will contain more than one primarily because they do not exist in pure form naturally. They must be “sourced” from various minerals. The exact chemical composition of the various minerals used in ceramic glazes helps to determine which material to use.

The most common glass maker is silica. Silica is also found in virtually all minerals including clay. It can also be found in a relatively pure form by powdering quartz. Boron is a secondary glass maker in addition to being a flux.

The most common intermediary material is alumina, and while it can be had in pure form, it is most often obtained from clay – the pure form being extremely expensive. The intermediary hardens and strengthens a glaze. The ratio of alumina to silica in a glaze will decide how shiny or matte the surface of the glaze will be. The more silica, the shinier the glaze will tend to be – as long as there is sufficient flux to maintain the melt.

Ideally, a glaze recipe will have as few ingredients as possible. The more materials in a glaze, the more issues that will tend to arise as various chemicals in the composition react with each other. Keeping things simple helps to avoid trouble.

Glazes have to be carefully formulated if they are to be used for dinnerware and everyday use. Formulas that are not properly balanced and hardened sufficiently may be prone to leaching; the gradual loss of glaze material into the food or liquid in contact with the pot. The leaching of lead – once the most popular flux in ceramics manufacturing – came to the fore a few decades ago when people were poisoned by food that had been stored in lead glazed pottery. That pottery was not manufactured in the USA (there has never been a case of lead poisoning from domestically produced pottery to the best of my knowledge), but the fact that lead is toxic and accumulates over time in the body has made its use in pottery manufacturing impossible. It is not even possible to obtain lead from ceramic suppliers any longer.

More on glazes in my next article!

Well, That Was the Kickstarter That Was

Posted on08.08.15 by Geoff Miller

New Sign

By now you may have heard that my long planned and highly vaunted Kickstarter campaign did not reach its goal. It was an ambitious – and probably unrealistic – goal, but you never know what’s possible until you try. That’s the attitude I had when I launched the campaign, and the one I still have. Fear not, I am not daunted.

So now what?

Well, there is always Plan B. Plan B came about several weeks before the Kickstarter launched and it continues to take shape. Simply put, Plan B involves approaching the bank with a business plan, getting their approval for a business loan, and then getting all the support I can from a different crowdfunding site. Specifically, I am looking into Indiegogo, which offers a number of different crowdfunding platforms. Among them is Flexible Funding, which means that you raise as much as you can but do not have to meet your stated goal. Since bank financing will guarantee the building gets built, Flexible Funding can not only assist in defraying that expense, it can help with the incidentals that come once the building is built.

What really buoys my spirits is the fact that some people have chosen to send monetary support for the building project even though the campaign didn’t end successfully. That money is being placed in a separate building fund and those who sent it will be entitled to the same rewards they would have received from the Kickstarter if they choose to claim them.

Another step I am taking is to keep in touch with my Kickstarter backers. Those who still wish to support the building project will be able to do so once the Indiegogo campaign is up and running. At this point, I know I can raise at least $10,000. The Kickstarter taught me that and it’s good to know.

And in the meantime, I am selling pottery from under a canopy on my front lawn. Why not? The sign is out, it is August 8, and today alone I have sold about $200 worth!

I’m keeping the faith.

Copyright 2015 - 2023 Lowell Hill Pottery. All rights reserved.