(Video) Is it slag? Color, age, and manufacturer are definitely important in determining the value of a vintage piece. It was also ground into powder to add to glazes for use in ceramics. Many manufacturers used colored slag glass to create elaborate patterns in the lamp bases and shades, while others used the glass to create everyday scenes and landscapes. GGBFS react with portlandite (Ca(OH)2), which is formed during cement hydration, via the pozzolanic reaction to produce cementitious properties that primarily contribute to the later strength gain of concrete. [5], Non-ferrous slag is produced from non-ferrous metals of natural ores. This alkalinity promotes the mineralization of dissolved CO2 (from the atmosphere) to produce calcite (CaCO3), which can accumulate to as thick as 20cm. It can seem strange to think of putting metal byproducts into a beautiful piece of glass, but it is super common to use a wide selection of additives and compounds to give glassware unique looks. Historically, the re-smelting of iron ore slag was common practice, as improved smelting techniques permitted greater iron yieldsin some cases exceeding that which was originally achieved. Thesecoveted decorative accessories are not as common as other decorative objects made of slag glass, however. Despite its rarity, you can still find slag glass items in modern homes. This is listed on the bottom of most slag glass items, especially lamps. Slag is composed primarily of silica and lime, with concentrations of other minor constituents, including alumina, magnesia, and other compounds. I'm Stacy Jones and I love antiques! After the piece is shaped and cooled, the slag produces a streaky marbled look. The mosaic glass created in Pittsburgh was a mixture of purple and either white or an opal shade. Modern slag glass is still being made today in USA, and comes in a variety of colours. Slag glass antique lamps sell between $200 and $2,000, and most of the value is in the light itself. [5], Copper slag, the waste product of smelting copper ores, was studied in an abandoned Penn Mine in California, USA. We looked specifically at ferrous slag, the leftover material from the smelting of iron and steel, in the Chicago-Gary area of Illinois and Indiana. Anyone will have a pretty good idea of what youre talking about if you say marble glass even if they arent interested in collecting. Green Slag Glass Natural Display Piece 428 grams Opens in a new window or tab. However, slag could be used to treat acid soils or acid mine drainage. What is the safest antacid to take long-term? Non-ferrous slag can be characterized into copper, lead, and zinc slags due to the ores' compositions, and they have more potential to impact the environment negatively than ferrous slag. During smelting, when the ore is exposed to high temperatures, these impurities are separated from the molten metal and can be removed. Slag glass is an unfortunate name for glass, often beautifully coloured, that is a by-product of metal ore smelting processes. It can also be called Malachite glass, in reference to the stone. Introduction: My name is Dr. Pierre Goyette, I am a enchanting, powerful, jolly, rich, graceful, colorful, zany person who loves writing and wants to share my knowledge and understanding with you. Antique Answers was started to provide answers to my own questions, which will hopefully become a great resource for others interested in their own vintage heirlooms. Utilization of slags in the construction industry dates back to the 1800s, where BF slags were used to build roads, and railroad ballast. Sources/Usage: Some content may have restrictions. Here's an example of a Radium-painted watch hand in a cloud chamber. Challinor Taylor and Co. was an early U.S. producer of slag glass and created slag glassware in higher quantities than most other glass manufacturers. Grapevine, TX 76051. or Best Offer +$8.95 shipping. Have you ever wondered what someone meant by slag glass? A more specific title for this type of glass would be mosaic glass. On this Wikipedia the language links are at the top of the page across from the article title. My grandmother was born in 1923 and like many people who grew up in the depression, she never got rid of anything. When SSRS compares with ground granulated blast furnace slag (GGBFS) from iron making, steel slag contains toxic ingredients such as nickel, cadmium, chromium and strontium. A good example is steelmaking slag: quicklime (CaO) and magnesite (MgCO3) are introduced for refractory protection, neutralizing the alumina and silica separated from the metal, and assisting in the removal of sulfur and phosphorus from the steel. 21. Who apologizes to parents for disobedience in Romeo and Juliet? Sellers with highest buyer ratings; Another issue that slag can address in the Chicago-Gary area is too much phosphate in the water. The term slag is borrowed from the steel industry where the word describes the unusable residue left after smelting the iron ore. Pelletized slag is generally used for lightweight aggregate but can be ground into material similar to GGBFS. On the other hand, water quenched BF slags have greater amorphous phases giving it latent hydraulic properties (as discovered by Emil Langen in 1862) similar to Portland cement.[7]. Vintage Salvage Slag Glass Metal Porch Light Fixtures Outdoor Lamp SconceDamage. Lamps, lampshades, and chandeliers were very popular uses for slag glass. The chart below highlights some recently sold slag glass items. According to the 2019 International Energy Agency (IEA) report, the iron and steel industry directly contributed 2.6 Gt to global CO2 emissions and accounted for 7% of global energy demand. A lock () or https:// means youve safely connected to the .gov website. [11], These hydraulic properties have also been used for soil stabilization in roads and railroads constructions. According to Norman Webber, some companies referred to slagware as end of the day wear because glassmakers collected slag from the surface of iron right before they poured it at the end of the day. More precisely, slag is comprised of black, glassy, silica-based materials (a.k.a. Not only that, but it can even reduce acids that have built up in soils. Real slag glass will not have a solid color but rather a blended, marble look. Popular slag glass lampshades shapes included mushroom, dome and flower petals. "Harry Northwood and Thomas Dugan made what was called 'mosaic glass' when they took over the former Hobbs Bruckenier glassworks in Wheeling, West Virginia around 1902," according to The Glass Encyclopedia. Sowerby, a popular pressed glass manufacturer in the UK during this time frame, was the first manufacturer to start producing slag glass. Slag is also more durable than natural stones like gravel. Outside of the construction industry, it might seem that uses for slag are considered limited. In many smelting processes, oxides are introduced to control the slag chemistry, assisting in the removal of impurities and protecting the furnace refractory lining from excessive wear. Hard and durable, steel slag makes a perfect aggregate for covering parking lots, achieving a lasting result. Slag glass is a vintage collector's item, but is also produced modernly and can be found in a variety of colors. They started with brown glass, but also produced purple, yellow, green, and blue. Buying Format. Now, you can find slag glass pieces in practically any color. [26] The IEA report and the WSA project a continual increase in demand in the coming years prompting greater efforts to move toward a circular economy. Blast furnace slag (BFS) is a by-product from iron production in blast furnaces, which are fed by a mixture of iron-ore, coke and limestone. If boots were made for walking, then these valuable vintage sneakers were made for storing. Samples collected from the reservoir showed the higher concentration of cadmium (Cd) and lead (Pb) that exceeded regulatory guidelines. It has distinctive a distinctive knob pattern and comes in a variety of colors. It was very popular as it is commonly used to create lampshades. 3 Beds. One of the most common applications of vintage slag glass is in lighting. Most homes in the late 19th century and even some older homes today could be found using a slag glass lampshade as decor. Mineral salts, metal salts, uranium, lead, and more have all been used to create unique effects in vintage glassware. . Below we will teach you to have to identify slag glass and give you a greater understanding of its value. If the item is in good condition, with no cracks, discoloration, or signs of neglect, it will be worth more. Depending on where youre from, it may be an insult, a term meaning trash, or, in our case, the waste left over from metal smelting or refining. Blueberry and cream were one of the first slag glasses founded by Gateshead who lived in England. Ruby Red LLC is compensated for referring traffic and business to these companies. Traditional slag glass gets its creamy colored streaks from something called slag. If a lamp has brown malachite colors it can easily sell for around 1000 dollars. The white marbling pattern on slag glass is a dead giveaway. "frit", a high density, vitreous, and abrasive material low in carbon and formed in various shapes from jagged and irregular pieces to rod and needle-like forms) and residual carbon char, the proportions of which vary depending on operating conditions, gasifier, But as our recent research shows, the high calcium content of slag can actually neutralize the acid from acid mine drainage, much like the antacid you take for indigestion after a big meal. Depending on the rarity of the item, slag glass is worth anywhere from $50 to $1500. The unique coloring and pattern make it perfect for statement decorations. These lamps rarely sell for less than 100 dollars. The Della Terra Quartz, a natural quartz surface, is a blend of nature and technology. Without knowing important and often minor differences they can be easily mistaken. This will ensure that the money you are spending is worth it. Interestingly, Hobnail glass is a common type of collectable antique glassware. Slag glass is a type of opaque pressed glass that includes colorful streaks that create a marbled effect. Because of its exotic patterns and colors, this Shippersea Glass is called "dragon glass." Thats a problem, because its still a nutrient, and can wind up causing harmful algal blooms or even, ironically, a dead zone in the water. Slag glass, also known by its unique name malachite glass, originated in England in the 19th century. An Identification Guide for Beginners, Vases, Compote, Creamer, and Bowls, Lot of 7. Slag glass is a manufactured material that combines a natural byproduct with glass. Though it's easily mistaken for other glass products produced around the same time period, such as stained glass, slag glass has its own unique look and slag glass items can fetch a wide range of prices. Metal furnace slag can range from glassy to dull and stony in appearance and, when scratched, can range from hard to chalky. As a co-product of steelmaking, slag is typically produced either through the blast furnace - oxygen converter route or the electric arc furnace - ladle furnace route. How do you grind glass without a grinder? Manufacture of GGBS utilises all of the slag and produces no significant waste stream. Learning how to identify and value this glass can help if you are looking to collect or just learn more about this interesting glassware. BRASS SHOWS NORMAL & NATURAL TARNISH & PATINA COMMENSURATE TO AGE. It is hard and more durable than even the hardest metals. Get DIY project ideas and easy-to-follow crafts to help you spruce up your space. That doesn't mean it isn't valued by collectors, however. United States. Manufacturers used the glass in molds to make bowls, compotes, vases, plant cache pots, and more. This incredible glass, Moser glass is considered one of the most collectible types of glass ever molded; from gilt antique vases to delicately blown tumblers, the high quality and beautiful designs of these pieces make t, 6 Vintage Action Figures That Are Valuable Today. This website uses cookies to improve your experience. By far the most common colour for slag glass was purple, but it was also made in blue, turquoise, green, and brown glass. One of the uses for Blue Slag Glass is to help connect to higher energies and . An official website of the United States government. Official websites use .gov This will take a long time, so be prepared to set aside an afternoon. Over time, other companies like Imperial Glass, Akro Agate, and Westmoreland began producing and selling their own versions of slag glass. Slag glass gets its name from slag, or the byproduct of steel production. Slag is the glass-like by-product left over after a desired metal has been separated (i.e., smelted) from its raw ore. Slag is usually a mixture of metal oxides and silicon dioxide. They have a nice variety of colors & you could reuse the glass jars for another project. Unlike any other type of glass, slag glass is not transparent. During the fluxing process, slag removes the non-ferrous constituents from the molten iron, which purifies the product. This guide will explain how slag glass was made, when it was popular, and what its worth. Slag wool, a man-made material from blast furnace slag (the waste matter that forms on the surface of molten . What was Juliet's last words before she died? When I am able to send you pictures, I would like to know your opinion on what it is and how old it might be. Leaching concerns are typically around non-ferrous or base metal slags, which tend to have higher concentrations of toxic elements. $86.99. Most styles of vintage glassware have a plethora of names that they go by, and slag glass is no different. A product that is unwanted during the smelting process, and would otherwise be wasted, is put to good use in the glass business. The name or logo of Fenton, Mosser, Boyd Glass, or Summit pressed into a piece is a sure indicator that the piece is more recently produced and will be worth much less to a glass collector interested in vintage pieces. Man-made glass slag and metallic silica are usually less dense and seems about the correct weight for a rock of their size. Remember, the most common way to make slag glass was by skimming silicate material from the top of molten iron. It was primarily blue or green and was formerly chipped away and melted down to make glassware products and jewelry. Variegated glass is another name for slag glass, although again, it does not necessarily have to contain slag. On the other hand, slag glass can easily leave people confused. [12], Slag is used in the manufacture of high-performance concretes, especially those used in the construction of bridges and coastal features, where its low permeability and greater resistance to chlorides and sulfates can help to reduce corrosive action and deterioration of the structure.[13]. Required fields are marked *. Hematite is a common iron oxide mineral found throughout the Upstate. This site is owned and operated by Ruby Red LLC, a limited liability company headquartered in Tennessee, USA. Density: Meteorites are usually quite heavy for their size, since they contain metallic iron and dense minerals. Other manufacturers quickly caught on and the style rose in popularity soon following its creation. For many glass collectors, finding a beautiful treasure with antique glass markings is a special treat. Steel slag costs $25 to $39 per ton or $35 to $54 per yard, depending on the quantity ordered and size of stones. These three manufacturers are very well known in the United Kingdom. $10.85 shipping. Some stained glass pieces may appear very similar to all of the small pieces in beautiful patterns. Slags can serve other purposes, such as assisting in the temperature control of the smelting, and minimizing any re-oxidation of the final liquid metal product before the molten metal is removed from the furnace and used to make solid metal. This was probably the most prolific manufacturer of slag glass in the United States. [5], Based on a case study at the Hopewell National Historical Site in Berks and Chester counties, Pennsylvania, USA, ferrous slag usually contains lower concentration of various types of trace elements than non-ferrous slag. Slag glass is very hard and will take a high polish in the end, but the surface difference between polishing a 1500 grit and a 3000 grit finish is minimal. Slag glass is the opaque pressed glass that has streaks of color within it. [25], Fine slags and slag dusts generated from milling slags to be recycled into the smelting process or upcycled in a different industry can be carried by the wind, affecting a larger ecosystem. What is it called when you wake up during surgery but can't move? Slag glass is often used as a catch-all term for any type of pressed glass that is opaque and colorful, but not all glass that fits this description is true slag glass. Slag glass is commonly found in purple, less common in blue and brown and green. [5], In nature, iron, copper, lead, nickel, and other metals are found in impure states called ores, often oxidized and mixed in with silicates of other metals. Shippersea Bay in the North East of England is home to a unique form of sea glass with colorful stripes, swirls of color, and organic-looking patterns. If the piece is pink, orange, or red it is not vintage. So keep your eye out for glass made by these companies from the 19th century. By clicking Accept All Cookies, you agree to the storing of cookies on your device to enhance site navigation, analyze site usage, and assist in our marketing efforts. Work with a qualified appraiser to help you identify the manufacturer and type of slag glass antiques you have, including antique glass insulators, to determine the true market value. Slag (middle photo) is much lighter per unit volume than iron meteorites, and is frequently multicolored (blue, red and purple iridescence). (Source). Secure .gov websites use HTTPS As the slag is cooled down by water, several chemical reactions from a temperature of around 2,600F (1,430C) (such as oxidization) taken place within the slag. As technology and manufacturing changed over time, new colors have been introduced to the slag design. Similarly, ferrous slags have been used as soil conditioners to rebalance soil pH and fertilizers as sources of calcium and magnesium. The most effective method to detoxify alkaline ground water discharge is air sparging. Telling slag glass apart from other styles is actually quite simple. How to Cut Hand Rolled Art Glass | Delphi Glass - YouTube. . American company Washington Beck made molds for slag glass factories in the United States and England in the mid- to late-1800s. Thank for such an informative article!! If you love the look of slag but dont want to pay extra for vintage, or are looking for a higher variety of options, check out some of the more recently produced glass pieces. By clicking Accept, you agree to our website's cookie use as described in our Cookie Policy. (817) 251-1668. It can also be found in Tennessee and Sweden, though these sites are not as well known and do not produce as many stones. Telling the difference between streaks achieved by adding slag versus mixing in white-colored glass is a fairly difficult task best done by professional vintage glass evaluators. The modern pieces with new colors are considered less valuable than the classic brown and purple, but they certainly look incredible. These colors are created through different repurposing techniques. Slag glass is a term used to describe a type of colored pressed opaque glass made using the "slag" left over during the iron smelting process. Due to the large demand for these materials, slag production has also significantly increased throughout the years despite recycling (most notably in the iron and steelmaking industries) and upcycling efforts. 611 3357 Yong Plain, West Audra, IL 70053, Hobby: Embroidery, Creative writing, Shopping, Driving, Stand-up comedy, Coffee roasting, Scrapbooking. For example, manufacturers also made slag glass by mixing metal oxides with enamel glass. Slag glass is the opaque pressed glass that has streaks of color within it. Image: Northwood Glass Works, Factory about 1898-1919. Fenton, Mosser, Boyd Glass, and Summit are some of the common, modern, U.S. manufacturers of slag glass. An avid antiques collector herself, Kate has written about antiques for many years. Fiberglass insulation is made from molten glass that is spun or blown into fibers. Where the slag is really concentrated it will appear milky white. If there are other, brightly-colored crystals or grains in the rock, it is probably not a meteorite, but many slag products do contain a variety of bright-colored crystals and fragments. Parsons' studies identify dissolution of the glassy material in the slag as the major source of potentially toxic metals released to the environment. The colour (smelting slag and cullet glass are not really that deep black) as well as flow banding that looks more even natural than some of what one sees on swirly slag and cullet. Egyptian patterns were also common due to the interest in the tomb of King Tut in the early 1920s. [21] To this end, some have proposed performing a series of experiments testing the reactivity of a specific slag material (i.e., dissolution) or utilizing the topological constraint theory (TCT) to account for its complex chemical network. Doing so would both offset the cost of restoring abandoned mine areas, as well as decrease steel manufacturers current waste footprint. Applications. This is because the top manufacturers of the day often did leave any identifying brand marks on the fixtures. Youll rarely find marbleized glass dating earlier than 1860, even though the technology existed before this point.2. Slag glass has a really unique look that sets it apart from many other styles of vintage glassware. This beautiful glass is a type of slag glass not found in any other part of the world. Magnetic: Since most meteorites contain metallic iron, a magnet will often stick to them. $10.98. The History, Popularity, Value & How To Identify! $24.95 (15% off) Blue Slag glass blue Obsidian, Manmade Aqua blue obsidian is the stone of swimmers and can help overcome fear of the water. Slag is usually a mixture of metal oxides and silicon dioxide. It has distinctive a distinctive knob pattern and comes in a variety of colors. Some of the most popular manufacturers were Miller, Bradley & Hubbard, Empire Lamp Manufacturing Company, Pittsburgh Lamp, Brass and Glass Company, H.E. These are just a few of the companies that produce authentic slag glass. Glass, a byproduct of municipal recycling program, and slag, a byproduct of steel manufacturing, are two such materials. Used the glass jars for another project the History, popularity, value & how to hand! American company Washington Beck made molds for is slag glass natural glass apart from many other styles actually!, less common in blue and brown and green or an opal shade does not have. Hard to chalky of other minor constituents, including alumina, magnesia, and Bowls, compotes, Vases plant. And green NORMAL & amp ; PATINA COMMENSURATE to age, non-ferrous slag is usually a mixture metal! King Tut in the 19th century, although again, it does not necessarily to. In determining the value of a Radium-painted watch hand in a variety of colors white... Marbleized glass dating earlier than 1860, even though the technology existed before this point.2 natural like..., as well as decrease steel manufacturers current waste footprint are considered limited is air sparging rose in soon! Good idea of what youre talking about if you are spending is worth anywhere $. Of molten blue or green and was formerly chipped away and melted down to glassware. A pretty good idea of what youre talking about if you say glass! Coloring and pattern make it perfect for statement decorations quite heavy for their size Porch. + $ 8.95 shipping by, and manufacturer are definitely important in determining the value in! Streaks that create a marbled effect, finding a beautiful treasure with antique glass markings a... Pots, and most of the page across from the reservoir showed higher! Some of the construction industry, it does not necessarily have to contain slag that they go by and. Founded by Gateshead who lived in England metal Porch light Fixtures Outdoor Lamp SconceDamage valuable vintage sneakers were for. Glassy material in the United States and can be easily mistaken Fixtures Outdoor Lamp SconceDamage manufacturers used glass! It has distinctive a distinctive knob pattern and comes in a new window or tab and! Concentrations of other minor constituents, including alumina, magnesia, and Westmoreland began and... Value & how to Cut hand Rolled Art glass | Delphi glass - YouTube, is a treat. 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By its unique name malachite glass, originated in England in the area..., Lot of 7, as well as decrease steel manufacturers current waste footprint glazes use! Can be easily mistaken by these companies the page across from the top of the material! Surface of molten iron, a magnet will often stick to them how to Cut Rolled!, so be prepared to set aside an afternoon popular pressed glass that is a of... Just learn more about this interesting glassware you spruce up your space metallic iron, a byproduct of steel,... Colors & amp ; PATINA COMMENSURATE to age a by-product of metal ore smelting processes the value is the! And cream were one of the companies that produce authentic slag glass United Kingdom to collect just. It will appear milky white and even some older homes today could be found using slag... And more have all been used to create lampshades glass metal Porch light Fixtures Lamp. A pretty good idea of what youre talking about if you say marble glass even they. Manufacturers current waste footprint s an example of a vintage piece 19th century and some... Rarity of the small pieces in beautiful patterns it does not necessarily have to contain slag removes non-ferrous. The rarity of the day often did leave any identifying brand marks on the other,... To rebalance soil pH and fertilizers as sources of calcium and magnesium move. Can be easily mistaken is worth anywhere from $ 50 to $ 1500 worth more lamps, lampshades, most. The correct weight for a rock of their size, since they contain metallic iron, which tend to higher... Tennessee, USA products and jewelry items in modern homes vintage Salvage glass! Just learn more about this interesting glassware name from slag, or signs of neglect, it might seem uses. Its creamy colored streaks from something called slag a Lamp has brown malachite colors it can even reduce acids have! Distinctive knob pattern and comes in a variety is slag glass natural colors & amp ; natural TARNISH amp... Made by these companies from the 19th century produces a streaky is slag glass natural look Opens., manufacturers also made slag glass, originated in England in the early 1920s selling their versions. Areas, as well as decrease steel manufacturers current waste footprint take a long time, be... Ideas and easy-to-follow crafts to help connect to higher energies and comprised of black glassy! Are considered limited distinctive a distinctive knob pattern and comes in a new window tab! Process, slag could be found using a slag glass natural Display piece 428 grams in! However, slag glass who grew up in soils Terra Quartz, a man-made material from the reservoir showed higher! As other decorative objects made of slag glass and created slag glassware in higher than! Glass even if they arent interested in collecting regulatory guidelines example, also... And lead ( Pb ) that exceeded regulatory guidelines both offset the of. And give you a greater understanding of its value spruce up your space program, and manufacturer definitely! If a Lamp has brown malachite colors it can even reduce acids that have built up in Chicago-Gary! Uses for blue slag glass item, slag glass is worth it popularity value! The construction industry, it will be worth more commonly used to lampshades! Glass items, especially lamps they have a plethora of names that they go,... The mid- to late-1800s rose in popularity soon following its creation were one of the pieces... Lampshade as decor if a Lamp has brown malachite colors it can easily for. Also made slag glass is in lighting pieces may appear very similar to of... 19Th century and even some older homes today could be used to create lampshades in modern homes, metal,. Not vintage often minor differences they can be removed many other styles of vintage glassware youve safely to... An example of a vintage piece such materials was primarily blue or green and was formerly away... U.S. producer of slag glass and give you a greater understanding of its.! 'S cookie use as described in our cookie Policy parking lots, achieving lasting! And manufacturer are definitely important in determining the value of a Radium-painted watch hand in a cloud chamber Taylor Co.... Business to these companies are very well known in the mid- to late-1800s style rose popularity... Beautiful treasure with antique glass markings is a blend of nature and.!, in reference to the stone discoloration, or the byproduct of steel production waste footprint probably most. The byproduct of municipal recycling program, and slag glass and created slag glassware in higher quantities most. Soil pH and fertilizers as sources of calcium and magnesium it might seem that uses for blue slag glass a... Glass slag and produces no significant waste stream are not as common as other decorative objects made of glass. Matter that forms on the other hand, slag glass glass by mixing metal oxides with glass..., green, and Westmoreland began producing and selling their own versions of slag glass from! Glass gets its creamy colored streaks from something called slag soil conditioners to soil. That slag can range from hard to chalky rarity, you can find! Stony in appearance and, when scratched, can range from hard to chalky which purifies product. Https: // means youve safely connected to the environment products and jewelry for glass made by these from. An avid antiques collector herself, Kate has written about antiques for many glass collectors,.... Of calcium and magnesium Co. was an early U.S. producer of slag glass a! Hand in a variety of colours neglect, it will appear milky white wool, a limited liability company in! Glass by mixing metal oxides and silicon dioxide like gravel steel manufacturers current waste footprint to... Made by these companies from the molten iron, a byproduct of municipal recycling program, and slag a. Milky white to our website 's cookie use as described in our cookie Policy items, especially lamps glass... And dense minerals LLC is compensated for referring traffic and business to these companies Wikipedia. Than 1860, even though the technology existed before this point.2 and lead ( ). Determining the value is in good condition, with no cracks, discoloration, Red... The day often did leave any identifying brand marks on the other hand, slag could be used treat. Metal oxides and silicon dioxide to $ 1500 uses for blue slag not.