I have just found these forums so excuse my question.

As a complete novice - no experience in this field whatsoever.
As a new project, I need to manufacture ceramic blocks ( about 4" x 2" x 1" perhaps slightly larger ).

These blocks must be porus, and able to absorb an oil based substance.

The exact porosity does not have to be rigourously repeatable and the blocks do not have to be exact in size or shape.

It should be based on readily available clay, formed and fired and low cost, without any specialised equipment aside from a kiln.

As I have never ever done this before, I am hoping for a simple answer and rough guide as to any special process to make the blocks porous ( if anything has to be done at all !!). So .. do I just buy any old clay and fire it and see what happens??

Here's hoping for a little starting advice ...

What is the oily substance? The raw material choice will probably depend on the chemical formula of this substance as there are many types of ceramic available.

Its basically an oil carrying a fragrance. I think it likely to be a refined vegetable oil.

We make porous ceramic blocks if you are just looking for the simple raw materials:

http://www.ictinternational.com.au/brochures/ceramicscatalogue.pdf

The pore size of a porous ceramic is of critical importance because it directly affects the ceramic's air entry value or
"bubbling pressure" and hydraulic conductivity. The air entry value is the pressure at which air will break through a
wetted pore channel. The hydraulic (liquid) conductivity of a porous ceramic is a measure of the rate at which a ceramic
material of known thickness may conduct liquid from one surface to an opposing surface under a known pressure. The
hydraulic conductivity will vary with the type of pore fluid used which is generally water, but can be oils or other natural
and artificial liquids. The effective pore size is determined by the minimum orifice within a channel or pore. These
properties that are determined by pore size are intrinsic to ceramics and to all other porous materials. How a porous
material behaves in any application is directly related to these pore properties and the material from which it is made.

Formulas or mixes (M) and associated Specific (B) Bar Values
B0.5 - 1/2 Bar (7.4 psi or 50 KPa) Air Entry Ceramics
Ceramic - B0.5M2
This ceramic is developed from a high fired, Alumina body. The resulting ceramic is an excellent material which is extremely porous, inert to most all solutions, possesses hard exterior and interior surfaces, and is pure white in color. This material is recommended for low pressure differentials not exceeding 7.4 psi. The tremendous porosity and high conductivity of fluids or gases make it ideal for quick extractions or in creating, monitoring or extracting pulse hydrological events. The material is ideal for liquid or gas sampling as the Alumina material has almost no ionic exchange sites or "leachable" mineralogy. This is a truly superior ceramic for both industrial and scientific work where high volume transfer or testing at low pressure differentials is necessary.

B01 - 1 Bar (14.7 psi or 100 KPa) Air Entry Ceramics
Ceramic - B01M1
This ceramic is developed from a moderately fired largely Talc body. The resulting ceramic material, made from a time proven formula, is a utilitarian ceramic having good porosity, tough exterior and interior surfaces, and is ivory white in color. This material is recommended for general purpose uses that involve pressure differentials under 15 psi. This ceramic is an excellent choice where cost and precise content of fluids or extracts are not at issue. This material has been applied successfully to tensiometers, pressure plate assemblies, suction tables and the like for nearly 50 years. This ceramic is not recommended for precision fluid sampling work as it has some ionic exchange sites and a mineralogy that is leachable with strong acids over the years. This is the perfect choice for those needing a low cost industrial ceramic product or where the science requires minimal fluid content determinations.

Ceramic - B01M3
This ceramic, like the B0.5M2, is developed from a high fired Alumina body. The resulting ceramic is an excellent material. It is extremely porous, inert to most all solutions, possesses hard exterior and interior surfaces, and is pure white in color. This material is recommended for standard pressure differentials not exceeding 15 psi. The tremendous porosity and ability to conduct large amounts of fluids or gases makes it ideal for quick extractions, and creating, monitoring or extracting pulse hydrological events. The material is ideal for liquid or gas sampling as the Alumina material has almost no ionic exchange sites or "leachable" mineralogy. A great material for most any application involving sampling, testing, monitoring or infusion where precision and actual liquid contents are of importance.

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B02 - 2 Bar (29.4 psi or 200 KPa) Air Entry Ceramics
Ceramic - B02M1
This ceramic is developed from a variety of ball clays into a moderately fired ceramic body. The fired product has an effective porosity and good hydrologic flow capability. Bubbling pressures for this ceramic are pressure differentials less than 29.4 psi. This general use ceramic is most often used on specialized plates for soil water retention or in unique oil and gas industries for reclamation studies. The material is moderately hard and creamy white in color. This ceramic is recommended for specialized applications using plates.

B02 - 2 Bar (29.4 psi or 200 KPa) Air Entry Ceramics
Ceramic - B02M2
This porcelain ceramic is developed from a high fire Silica body. The resulting ceramic is an excellent material for slightly elevated pressure differentials not exceeding 29.4 psi. The material has a somewhat grainy texture and pure white appearance. A good material for sampling fluids and gases as porcelain has few ionic exchange sites or "leachable" mineralogy. With the good porosity and hydrologic characteristics, this ceramic provides a material that can be used by oil companies or agricultural research scientists. This ceramic is an excellent choice for those needing the added capacity of elevated pressure differentials and precise fluid content measurements.

B03 - 3 Bar (44.1 psi or 300 Kpa) Air Entry Ceramics
Ceramic - BO3M1
This ceramic is developed from a complex mixture of ball clays into a moderately fired ceramic body. The resulting ceramic has good porosity and good hydrologic flow capability. Bubbling pressures for this ceramic are pressure differentials exceeding 44 psi. This ceramic is generally used within pressure vessel equipment for the determination of soil water retention or in oil and gas industries for reclamation studies. The material is moderately hard and tannish-white in color. This ceramic is recommended for specialized applications where the differential pressures will be less than 44 psi.

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B05 - 5 Bar (73.5 psi or 500 Kpa) Air Entry Ceramics
Ceramic - B05M1
This ceramic, like the "B03M1", is developed from a complex mixture of ball clays into a fired ceramic body. The resulting ceramic has good porosity and good hydrologic flow capability. Bubbling pressure or air entry values are pressure differentials exceeding 74 psi or greater. It is generally used within pressure vessel equipment for the determination of soil water retention or in oil and gas industries for reclamation studies. The material is very hard and brownish-white in color. This ceramic is recommended for specialized applications where the differential pressures will be less than 74 psi.

B15 - 15 Bar (220.5 psi or 1500 KPa) Air Entry Ceramics
Ceramic - B15M1
This ceramic is developed from a proprietary mixture of ball clays fired to a ceramic body. The resulting ceramic material is pinkish-tan in color, moderately hard and will withstand pressure differentials of 220 psi. This unique ceramic, incorporated into 0675 pressure plate cells, has been used in Agronomy for many years in water retention studies to a theoretical wilting point of 15 bars. It has also found use in the oil and gas industries in studies of reclamation and production techniques. It remains the worldwide choice of experts when they need to know the behavior of liquids to a 3 dimensional porous material that mimics soil and stone. The B15M1 is still the only ceramic in the world that, when wetted, can withstand a pressure differential of 220 psi and not leak or bubble. The unique characteristics of the B15M1 ceramic make it the selection of experts and scientists who are involved in liquid movements and transfer conditions at elevated pressure differentials.

NOTE: Formulas and Mixes
The above formula descriptions for our ceramics are keyed to the "bubbling" (B) or air entry value of a ceramic. There may be one or more "mixes" (M) associated with a particular air entry value. M1 will denote the first formula, M2 the second, and so forth. An example of this non-relationship: M1 mix for a B1 (one bar air entry value) is not in any manner related to the mix or formula M1 for a B5 (five bar entry value ceramic).

Interesting Reese.

I will look at this. My primary goal would be to make ( have made ) blocks in smallish size as per my original mail.

I have no idea what these would cost commercialy. They do not need to be technically perfect - just porous to soak up the fragrance.
I realise that different porosities will soak up the oil at different rates - but likewise they will release the fragrance at different rates too. All this will be experimental.

My initial reaction was to make them in-house, using what might be a simple technique.

I would be spending a lot of time messing about with clay and a kiln unless I can find out what may be a well know principle. Maybe I need to do a lot more background reading!!

Here is one of the early recipes:

US Patent 4447548

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to scented materials and more particularly to ceramic type scent carriers.

2. Description of the Prior Art

A great many materials have been used for carrying scents. For example, Carson in U.S. Pat. No. 4,254,179 and Stone in U.S. Pat. No. 4,226,944 both teach processes for impregnating a porous foam product with fragrance. Foams, particularlypolyurethane foams, are well adapted as fragrant carriers due to their high porosity and cellular impermeability. Disruption of the cell structure of the foam allows a fragrance to escape through the porous network of the foam.

Another type of scent carrier is taught in U.S. Pat. No. 4,110,261 of Newland which describes a fragrance emitting article having a polymer-petroleum wax composition. Wax based scent carriers differ from foam carriers in that they do not havepores or intersticies which would allow the fragrance to escape. Fragrances are typically released from a waxed based carrier by partially melting it or by scratching its surface.

Yet another approach to scent carriers is described in U.S. Pat. No. 4,293,602 of Coffey. In his patent, Coffey teaches a fragrant ornament consisting of a mixture of natural botanical materials, essential oils, and a fluorocarbon resinbinder. The resin binder holds the plant material together and slows the release of the essential oils.

A substantially different approach to scent carrying was taken by Atkinson in U.S. Pat. No. 195,324. In his patent, Atkinson describes a fragrant article made from a porous ceramic soaked in a perfumed oil. The article can be worn as a charmor an ornament such that the perfume is released over a period of time.

Of all of the above cited patents, only Atkinson addresses the problem of applying a scent to a hard, immalleable, and stable material. Obviously, the foam, wax, and resin based scent carriers described above are rather fragile materials and aresubject to rapid wear and structural failure. On the other hand, Atkinson's ceramic based scent carrier, if properly fired and cured, can be quite durable and should last many years in normal usage.

Atkinson's article, however, does have certain drawbacks. The rather low absorbtion ability of commercially available ceramic materials means that the articles described by Atkinson cannot hold very much perfume. This, of course, means that hisarticles will rapidly lose their scent. Furthermore, since commercially available ceramic materials have a moderately high specific gravity of about 1.77, they tend to make rather heavy and clumsy ornaments.

SUMMARY OF THE INVENTION

An object of this invention is to provide a improved scent carrier.

Another object of this invention is to provide a high porosity, low density ceramic material well adapted for carrying scented fluids.

Yet another object of this invention is to provide several methods for producing the low density ceramic material.

A still further object of this invention is to provide a high porosity ceramic material with a very high fluid carrying capacity per unit weight.

Another object of this invention is to provide a ceramic material which has a high fluid carrying capacity per unit volume.

Yet a further object of this invention is to provide a scented ceramic material which will release a fragrance for an extended period of time.

Briefly, a method of the present invention is to (1) wet a finely divided, non-crystalline, amorphous silica with a volatile wetting agent; (2) combine the wetted silica with a commercially prepared ceramic slip to produce a mixture; and (3)remove the majority of the wetting agent from the mixture to produce a solid, low-density, highly porous bisque. A preferred wetting agent is distilled water, which is later removed by firing the mixture in a kiln. Preferably, one to four parts wettedsilica are combined with each part of ceramic slip.

Structurally, the scented ceramic material includes a low-density, high porosity bisque made from a mixture of a finely divided, non-crystalline amorphous silica and a ceramic slip, the resulting bisque being saturated with an aromatic fluid. Aportion of the surface of the bisque may be glazed to inhibit the evaporative dispersion of the aromatic fluid.

An advantage of this invention is that the bisque produced by the disclosed method has a very high fluid carrying capacity per unit weight and volume. Laboratory tests comparing the fluid capacity per weight of the high porosity bisque versusthe fluid carrying capacity per weight of a standard bisque indicates a increase of 514.29% for the present invention.

Another advantage of this invention is that the high porosity bisque has a very low specific gravity, and as such is well suited for wearing as a lightweight ornament.

A still further advantage of this invention is that a given volume of the high porosity bisque will retain an essential scent much longer than a conventional bisque.

These and other objects and advantages of the present invention will no doubt become apparent upon a reading of the following descriptions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The high porosity ceramic material of the present invention includes two essential ingredients, namely (1) a ceramic or porcelain slip; and (2) a finally divided, non-crystalline, amorphous silica.

The primary ingredient of most ceramic and porcelain slips is China clay (Kaolin). China clay is a soft white earth consisting principally of mineral kaolinite, which is a hydrated aluminum silicate (Al.sub.2 O.sub.3 2SiO.sub.2 2H.sub.2 O). Inits natural state, however, it invariably occurs with some of the alumina replaced by iron, titanium, and alkalis. Because it was first used in England for the production of Chinaware, it was given the English name China clay. In other countries it isusually called Kaolin.

Porcelain and most other types of ceramics are mixtures of Kaolin and other materials. For example, procelain is made by mixing Kaolin with other materials such as quartz, feldspar, or bone ash. The generic terms "ceramic" and "ceramic slip"will be used here to describe all Kaolin based materials, as well as other commercially available synthetic clays.

In ceramics, it is usual to suspend the Kaolin and the other materials in water to produce what is known as a ceramic slip. The slip material is usually poured into a mold, and then fired to produce a solid article known as a bisque or bisquit.

The amorphous silica used in this invention is usually synthetically produced to insure uniformity. The amorphous form of the silica differentiates it from crystalline forms of silica such as quartz, cristobalite, and tridymite. Synthetic,amorphous silica used in this invention should be analyzed for crystalline forms by X-ray diffraction techniques and, within limits of detection (0.3%), no crystalline forms should be found.

Synthetic amorphous silica is a substance that is inert both chemically and biologically. There is no history of systematic poisoning or silicosis related effects from exposure to amorphous silica. Thus, amorphous silica can be safely used inarticles that are subject to frequent human contact.

One manufacturer of amorphous silica is W. R. Grace and Company based in Baltimore, Md. The amorphous silica, which is produced under the trademark SYLOID, is used as a flatting agent, an anticaking agent, and for various other purposes.

A preferred method producing the high porosity material of this invention includes the steps of wetting the amorphous silica with a wetting agent, combining the wetted silica with a ceramic slip producing mixture, and removing the majority of thewetting agent to produce a solid, low-density, highly porous bisque. Preferably, the wetting agent should be fairly volatile so that it can be easily removed. When the wetting agent is removed by a rapid evaporative process such as kiln drying, waterhas been found to be a satisfactory wetting agent.

Preferably, the silica is saturated with the wetting agent to its maximum fluid carrying capacity. This prevents absorption of fluids from the commercial slip mixture and possibly ruining the mixture.

A portion of the surface of the bisque may be treated to reduce its permeability. This treatment can consist of coating a portion of the bisque with a substantially impermeable layer, such as by glazing techniques well known to those skilled inthe art.

As a final step, an aromatic fluid is applied to an exposed surface of the bisque for absorbtion into the body of the bisque.

It has been empirically determined that the proper volumetric ratio between the silica and the ceramic slip should be in the range of 1-4 parts silica to each part of slip. Mixtures outside of this range tend to produce a bisque that is eitherstructurally unstable or which possesses inadequate liquid absorption capabilities.

The following are two examples of the present method for producing a highly porous bisque.

EXAMPLE 1

(1) Combine the amorphous silica with a volatile wetting agent until it is fully saturated. Decant any excess wetting agent from the silica.

(2) Combine one part of the wetted silica with one part ceramic slip and mix thoroughly.

(3) Pour the mixture of wetted silica and ceramic slip into a suitable mold.

(4) Let the mixture sit until it has skinned over.

(5) Remove the skinned mixture from the mold.

(6) Air dry the mixture until a dry, hard bisque is formed.

EXAMPLE 2

(1) Pour amorphous silica into a receptacle containing distilled water until all of the water is been absorbed.

(2) Combine four parts of the wetted silica with one part ceramic slip and mix thoroughly.

(3) Pour the resultant mixture into a mold.

(4) Kiln dry the mixture at a temperature greater than 1200.degree. F. until the majority of the water has evaporated from the mixture.

(5) Remove the bisque from the mold.

The ceramic material resulting from the above methods results in a stable, relative inert substance well suited as a scent carrier. The ceramic material can be formed into ornaments, or into larger objects such as ash trays, lamp bases, plates,etc.

Tables one and two below compare the characteristics of the high porosity bisque of the present invention with a conventional bisque produced from ceramic slip alone. Table 1 compares the specific gravity, fluid capacity, and fluid capacity perunit weight of a conventional bisque and a high porosity bisque. All comparisons were made on fired materials having a volume of one cubic centimeter.

The specific gravity (measured in grams/CM.sup.3) of a conventional bisque is 1.77 as compared to a 0.82 specific gravity for a high porosity bisque. Thus, the change in specific gravity may be calculated to as 46.33% for the tested samples. Itshould be noted that the high porosity bisque has a lower specific gravity than water, and thus will float until water is absorbed into its body.

The fluid capacity of a conventional bisque was found to be 0.26 grams/CM.sup.3 as compared to 0.62 grams/CM.sup.3 for the high porosity bisque. This is an increase of 238.46% for the high porosity bisque.

Even more impressive is the fluid capacity per unit weight. This ratio is found to be 0.147 for a conventional bisque and 0.756 for a high porosity bisque, which is an increase of 514.29%.

As might be expected, the greater fluid carrying capacity of the high porosity bisque allows it to retain and release a fluid over a much longer period of time. Referring to table 2, the fluid retention of a conventional bisque in grams/CM.sup.3was measured to be 0.26 at time 0; 0.16 after one hour; 0.06 after two hours; and negligible after three hours. This compares to a 0.62 retention at time 0 for the high porosity bisque; a 0.52 retention after one hour; and measurable amount of fluiduntil eight hours later. As noted in the percent change column, the difference in fluid retention between the high porosity bisque and the conventional bisque increases rapidly with time.

TABLE 1 ______________________________________ CONVEN- HIGH TIONAL POROSITY BISQUE BISQUE % CHANGE ______________________________________ Dry Weight 1.77 .82 -46,33% Grams/CM.sup.3 Fluid capacity .26 .62 +238.46% Grams/CM.sup.3 FluidCapacity .147 .756 +514.29% Per Unit Weight ______________________________________

TABLE 2 ______________________________________ Fluid Retention Conventional Fluid Retention % Time (Hours) Bisque Grams/CM.sup.3 High Porosity Change ______________________________________ 0 .26 .62 +238.46% 1 .16 .52 +325.00% 2 .06.42 +700.00% 3 .0 .32 -- 4 -- .22 -- 5 -- .14 -- 6 -- .09 -- 7 -- .07 -- 8 -- .04 -- 9 -- .0 -- ______________________________________

While this invention has been described in terms of a few preferred embodiments, it is contemplated that persons reading the preceding descriptions will realize various alterations, permutations and modifications thereof. It is thereforeintended that the following appended claims be interpreted as including all such alterations, permutations and modifications as fall within the true spirit and scope of the present invention.