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Anvils in America - THE anvil book.

Blacksmithing and metalworking questions answered.

International Ceramics Products

High Temperature Refractory Blanket

Kaowool ®, Refractory Blanket:

High Temperature Refractory Blanket:

Kaowool, Cerablanket, Superwool Kaowool® is the original synthetic asbestoes replacement invented by Babcox and Wilcox the boiler and nuclear power plant builders. The product is now made by an offshoot company Thermal Ceramics, now Morgan Thermal Ceramics.

Over the years "kaowool" has become a generic term for refractory blanket like Coke for "Coca Cola" was for any soft drink or a Ford was for any automobile. In fact it is used interchangably for many trademark brands, UNIFRAX Durablanket, Haberson-Walker Inswool, NuTec Max-Wool. . . Then there are the sub-brands, Kaowool B, Cerawool, Kaowool S, Kaowool RT, Cerablanket, Cerachem, CeraChrome, SuperWool,
Refractory blanket is made from kaolin that is melted and formed into long fibers which is then formed into a mat then "needled" (sewn or quilted without thread). Lower grade product is a crumbly mat while the higher "high purity" grades are a strong resiliant blanket.

While kaowool is NOT asbestoes it does contain silica which can cause silicosis if inhaled in large quantities. After 30 years of use the kaowool fibers themselves have also been found to be possible carcinogens IF ground fine enough and sufficient quantity is inhaled. In use new bkanket is not a huge problem but after long periods of high temperature use the blanket breaks down producing fine particles. So more care is needed in repair and rebuild situations than for new instalation.

We recommend coating the interior of forges and furnaces with a refractory coating like ITC-100HT. This increases the blanket's temperature resistance, reduces dust, protects the blanket from mechanical damage and in the case of the ITC product increases furnace efficiency.

Material Mfg.
NuTec UNIFRAX Haberson-Walker Morgan Thermal Ceramics
Property Max-Wool HPS Durablanket S Inswool HP Cerablanket Kaowool
Melting Point 3200° F.
Class Temperature 2300° F. 2300° F. 2300° F. 2400° F. 2300° F.
Continous Use Limit 2200° F. 2150° F. 2150° F. 2150° F. 2000° F.
Alumina/Silica ~47 / 53 ~45 / 55 54 / 45 54 / 46 45 / 50-55
Iron trace 0.02% 0.2% trace 1.0%
Published Manufacturer's data. Compiled by DEMPSEYS FORGE /

There are higher temperature grades of refractoy blanket rated for 2500 to 2600°F. But these technical grades of blanket are generally very expensive and hard to get (not stocked). They are generally not necessary for propane and natural gas furnaces.

Why we no longer carry "Kaowool" brand blanket:

We have sold Thermal Ceramics blanket (Kaowool and Cerablanket) for almost 20 years and have no complaints about the product. However, in recent years the manufacturer has treated their distributors poorly, had annual shortages and tried to force Chinese made product on us. While there is nothing wrong with the Chinese product, American foundries generally will not buy it on principle and WE stand behind these principals as well. About half the product we were delivered was made in Mexico, take it or leave it.

We now carry NuTec Max-Wool HPS. It is made here in North Carolina in a modern new factory. The product is generally high quality in strength, texture and lower shot (crystaline grit). It is also lower cost which will be reflected in our prices as we sell off all our old inventory.

Max-Wool HPS is equivalent to or superior to the Cerablanket we have sold for years. If you look closely at the chart above you will see the contunous use rating is higer but the "class" temperature is lower. Both these values are subject to "fiddling" by the manufacturers so should be taken with a grain of salt.

About Superwool:

This is another Thermal Ceramics product. Superwool 607 HT low biopersistence ceramic insulation blanket. The 2372°F (1300°C) Classification temperature on this blanket is an absolute maximum compared to the other Thermal Ceramic products which were rated conservatively and can be used at higher than their rated temperatures. Due to this limitation we do NOT recommend this product for use in forges or where there is direct flame impingement. Our testing showed shrinkage and cracking at moderate forge temperatures.

We no longer carry this product due to slow sales.

References and Links

NuTec MasWool Refractory Blanket banner

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