miquel Posted January 8, 2013 Author Share Posted January 8, 2013 (edited) Edited January 8, 2013 by miquel Link to comment Share on other sites More sharing options...
miquel Posted January 8, 2013 Author Share Posted January 8, 2013 Miquel, That is quite amazing! I cannot agree more with your statement " Any excuse to learn something new and experiment with something interesting". That path may be a little slower, but much more valuable. Jan To tell you the truth, we made many mistakes but we learned a great deal from them. miquel. Link to comment Share on other sites More sharing options...
ZebDeming Posted January 8, 2013 Share Posted January 8, 2013 Metal molds, in my limited expirence, have been tricky. I have seen some folk smoke the mold to leave a thin layer of carbon, but they were on thicker steel molds and not sheet metal. Maybe even a thin painting of ceramic slip may help? Zeb Link to comment Share on other sites More sharing options...
VaughnT Posted January 9, 2013 Share Posted January 9, 2013 Fascinating. Truly a pity that there's so much to learn and only so much time on this earth to learn it! Can't wait to see how this pans out. I would never have guessed that the square tube was better, and not just an example of artistic license or easier manufacturing with the technology of the day. I'm thinking that sooting the inside of the mold might help prevent sticking of the copper. What about using a wax with a lot of coal dust mixed in? Or, pour a thick flat sheet of copper and then work it around a mandrel to make a hollow cone...... When reason fails... Link to comment Share on other sites More sharing options...
miquel Posted January 9, 2013 Author Share Posted January 9, 2013 I just thought I'd add a quick comment about moisture and iron oxides. Ancient Greek potters used an oxidation/reduction/oxidation firing to get their black and red ware. The reducing atmosphere was produced by closing the flues and piling in green wood. The wood not only burned incompletely, but let vast quantities of moisture into the kiln which causes a reaction turning FeO to Fe3O4. Thank you for your comments. We can talk about this later after we present the final results. miquel. Link to comment Share on other sites More sharing options...
miquel Posted January 9, 2013 Author Share Posted January 9, 2013 (edited) 1 ----- ZebDeming Posted Yesterday, 08:23 PM Metal molds, in my limited expirence, have been tricky. I have seen some folk smoke the mold to leave a thin layer of carbon, but they were on thicker steel molds and not sheet metal. Maybe even a thin painting of ceramic slip may help? Zeb ------------------------------------------------------------------ --------='VaughnT' date='09 January 2013 - 04:54 Fascinating. Truly a pity that there's so much to learn and only so much time on this earth to learn it! Can't wait to see how this pans out. I would never have guessed that the square tube was better, and not just an example of artistic license or easier manufacturing with the technology of the day. I'm thinking that sooting the inside of the mold might help prevent sticking of the copper. What about using a wax with a lot of coal dust mixed in? Or, pour a thick flat sheet of copper and then work it around a mandrel to make a hollow cone...... --------------------------------------------------------------------------------------------- ------------------------------------------------------------------------------------------------- All those precautions are good, but the problem with the copper soldering to the metal is not the only trouble of using metal molds that we encountered. miquel. Edited January 9, 2013 by miquel Link to comment Share on other sites More sharing options...
miquel Posted January 9, 2013 Author Share Posted January 9, 2013 (edited) For the next attempt we use a sand mold with an iron core. We prepared the sand for the mold using silica sand, bentonite clay 8%. We mixed everything dry then added water with constant agitation to promote good mixing and being careful to add just the minimum amount of water that would produce a mixture that could be compacted easily by hand. We made a container out of wood in two halves. The dimensions of the tuyere were 2.75" inches diameter at one end and 1.75" at the other with a total length of 20". We dusted the tuyere positive with talc powder to keep the sand from sticking to it when creating the negative. miquel. Edited January 9, 2013 by miquel Link to comment Share on other sites More sharing options...
miquel Posted January 9, 2013 Author Share Posted January 9, 2013 (edited) The two halves of the mold ready to insert the iron core. Edited January 9, 2013 by miquel Link to comment Share on other sites More sharing options...
miquel Posted January 9, 2013 Author Share Posted January 9, 2013 The iron core dimensions were 2", 1" and 20" long with extensions for support at both ends. miquel. Link to comment Share on other sites More sharing options...
miquel Posted January 9, 2013 Author Share Posted January 9, 2013 We placed the core in the mold. Closed the mold, placed the sprues and we were ready to go. The copper is already poured. Link to comment Share on other sites More sharing options...
miquel Posted January 10, 2013 Author Share Posted January 10, 2013 A bit of a disappointment... miquel. Link to comment Share on other sites More sharing options...
miquel Posted January 10, 2013 Author Share Posted January 10, 2013 (edited) Due to the stress during the contraction of the copper upon cooling over an incompressible iron core, the copper shattered in several places. miquel. Edited January 10, 2013 by miquel Link to comment Share on other sites More sharing options...
miquel Posted January 10, 2013 Author Share Posted January 10, 2013 (edited) We ended up with a shorter tuyere than we expected, better than the first but not there yet... miquel. Edited January 10, 2013 by miquel Link to comment Share on other sites More sharing options...
miquel Posted January 10, 2013 Author Share Posted January 10, 2013 (edited) Upon reaching this point we came to the realization that we only had one other option which was to use a core made of silica sand. We were advised to use a mix of silica and sodium silicate hardened using CO2. It sounded complicated to build but after a few tests we went for it. We made a negative mold of the iron core using plaster. We used it to measure how much silica sand we needed for the core. Edited January 10, 2013 by miquel Link to comment Share on other sites More sharing options...
miquel Posted January 10, 2013 Author Share Posted January 10, 2013 (edited) We weighted the sand calculating the addition of 7% of sodium silicate and mixed those two components in a bag. miquel. Edited January 10, 2013 by miquel Link to comment Share on other sites More sharing options...
miquel Posted January 10, 2013 Author Share Posted January 10, 2013 To keep the mix from sticking to the plaster mold we applied a coat of graphite. miquel. Link to comment Share on other sites More sharing options...
miquel Posted January 10, 2013 Author Share Posted January 10, 2013 (edited) Then we packed the mix in each half of the plaster mold. You can't see it in the pictures but each half is reinforced with a wire from one end to the other. We also set a string through the center when packing the sand. This string will be removed later and we will use the tunnel left by the string to flow CO2 to harden the mix. miquel. Edited January 10, 2013 by miquel Link to comment Share on other sites More sharing options...
miquel Posted January 10, 2013 Author Share Posted January 10, 2013 Then we joined the two halves together and gently tapped on then to promote the joining of the two halves. Insert them in a plastic bag and pump CO2 inside, wait 15 minutes then the mold can be taken apart carefully. miquel. Link to comment Share on other sites More sharing options...
ZebDeming Posted January 10, 2013 Share Posted January 10, 2013 Depending on how fragile your core is, you may want to consider setting up the mold vertical instead of horizontal for the pour Zeb Link to comment Share on other sites More sharing options...
miquel Posted January 10, 2013 Author Share Posted January 10, 2013 We were very surprised to see how solid the core was. We also considered using a vertical mold but we were advised by experts to use a horizontal one. The molten metal flows more evenly that way and the gases exit the mold with more ease. miquel. Link to comment Share on other sites More sharing options...
miquel Posted January 10, 2013 Author Share Posted January 10, 2013 (edited) We reused the previous mold for the outside. And followed the same steps. miquel. Edited January 10, 2013 by miquel Link to comment Share on other sites More sharing options...
miquel Posted January 10, 2013 Author Share Posted January 10, 2013 This time using the hardened silica sand core. Here everything is readied while the metal becomes molten. miquel. Link to comment Share on other sites More sharing options...
miquel Posted January 10, 2013 Author Share Posted January 10, 2013 (edited) miquel. Edited January 10, 2013 by miquel Link to comment Share on other sites More sharing options...
miquel Posted January 10, 2013 Author Share Posted January 10, 2013 Opening the mold. miquel. Link to comment Share on other sites More sharing options...
miquel Posted January 10, 2013 Author Share Posted January 10, 2013 miquel. Link to comment Share on other sites More sharing options...
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