Refractory coating

Discussion in 'Furnaces and their construction' started by NewBootGoofin, May 2, 2021 at 3:48 PM.

  1. Greetings all! I just got my first melting furnace and I’m excited to start this cool new hobby.

    The furnace I got is from a place called simond store. I mixed up the refractory coating according to the directions but it seemed like it lacked thickness. I applied it anyway yesterday. The insulation in the furnace is crispy but still kind of soft and have plenty of give to it.

    How solid is the insulation supposed to be after applying the coating?
  2. Tobho Mott

    Tobho Mott Gold Banner Member

    Welcome to the forums!

    There are all sorts of different refractories and insulation that can be used to build a melting furnace. Can you describe and/or name the product or products that came with your kit? Post lots of pictures and describe what you have done so far, then someone will be able to help more.

  3. Al2O3

    Al2O3 Administrator Staff Member Banner Member

  4. Melterskelter

    Melterskelter Gold Banner Member

    I see the sell refers to “rigidizer” in the ad on eBay. Most likely that is the applied coating. It can only be expected to make the surface a bit firm or crispy. If you read over various furnace build threads you will see reference to a coating called Satanite that imparts a firmer coating and is good for aluminum, brass, and bronze furnace interiors.

  5. Tobho Mott

    Tobho Mott Gold Banner Member

    That's odd, I see a furnace with 1" thick ceramic fiber blanket lining that comes with rigidizer when I click the link.

    "refractory coating [...] seemed like it lacked thickness. I applied it anyway yesterday. The insulation in the furnace is crispy but still kind of soft and have plenty of give to it."

    This may be a good description of how rigidized ceramic fiber is supposed to be, but I have not worked with rigizider so I could not say for sure.
    Edit - Denis beat me to it

  6. oldironfarmer

    oldironfarmer Silver Banner Member

    Have you fired it yet? The Heat Guard looks more like Satanite. You don't have to mix rigidizer. You do have to mix the other products. After firing it will become more rigid. Satanite goes on thin and fires to a very hard durable finish.

    Ceramic fiber which has been fired becomes very brittle. The fine glass fibers which will float in the air if you touch a fired ceramic fiber coating are hazardous and are treated like asbestos in industry.

    You need a coating to avoid releasing the fibers into the air. Also, avoid touching the ceramic fiber with a tool or crucible to avoid both damage to the coating and release of airborne fibers. Rigidizer and Satanite and products like Satanite do a great job of protecting the surface of the blanket from releasing fibers. Below that protected surface are millions of brittle dangerous glass fibers which are not protected if the protective layer is broken.

    Should you decide to replace the blanket in the future do that outside wearing gloves and a respirator. If you do it inside you will contaminate the space with the fibers and will create a hazardous atmosphere. This includes later when you sweep the floor and stir them up. Doing it outside you can wash down the area to flush the fiber away. Once they are wet they will not longer pose a hazard to your lungs. Immediately double bag the used fiber and wash yourself and your clothing. Just like asbestos, don't smoke or eat while you may be contaminated. Blowing out a "clean" furnace with an air nozzle is also a very risky activity.

    Ceramic fiber is a great product and makes a low mass, well insulated furnace which will heat quickly. Just recognize the dangers which are not so obvious.
  7. Melterskelter

    Melterskelter Gold Banner Member

    Concerning the dangers associated with ceramic fiber. There has been a long-held "concern" that ceramic fibers may be cancer causing or may cause respiratory harm. I suspect much of this concern is a carry-over from the well established carcinogenic effects of high intensity exposure to some forms of asbestos. Perhaps by reading the abstracts of the following papers may give a background against which users can decide on their own level risk aversion.

    The bottom line is that in industrial users there has been no link yet found in humans in real-world exposure to ceramic fiber as opposed to animal studies involving extremely high exposures. There has been a link in industrial users to chronic cough and decrease in lung function. There is suspicion that the fibers could be cancer causing in industrial exposures. And I think it is good to remember, for comparison, that alcohol which is widely used by the general population is a registered and confirmed carcinogen.

    My take is that for home foundry folks there is minimal risk of adverse outcomes in the sort of exposure which we are likely to experience. Yes, avoid high level prolonged exposure in enclosed areas. But, otherwise just be reasonably careful. There are other things we do in everyday life that are far more risky.: who manufacture,wheezing, and chronic cough).
    Studies of workers who manufacture RCFs have shown a positive association between increased exposure to RCFs and the development of pleural plaques, skin and eye irritation, and respiratory symptoms and conditions (including dyspnea, wheezing, and chronic cough). In addition, current and former RCF production workers have shown decrements in pulmonary function.

    Regarding alcohol:
    "Alcohol use is one of the most important preventable risk factors for cancer, along with tobacco use and excess body weight. Alcohol use accounts for about 6% of all cancers and 4% of all cancer deaths in the United States. Yet many people don’t know about the link between alcohol use and cancer."


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