czechfilip Posted January 4 Posted January 4 Hi, some recipes I read contain red gum. I know that it is a type of tree resin and I know there is a topic somewhere on here for possible red gum substitutes. I was just wondering if I can also use colophony as a substitute or should I stick to phenolic resin. Colophony is a lot cheaper for me. Thanks a lot
CountZero Posted January 4 Posted January 4 You might be able to replace it with shellac, but that tends to be (more)expensive).
PyroGnome Posted February 14 Posted February 14 (edited) You'd need to look at various formulas using it to get some idea of what kind of value it has as a binder & fuel. https://www.fireworkscookbook.com/recipes/?_recipe_search_ingredient_1=1627 There aren't very many, some from baechle system 4 & 5. The newest one is a green pillbox formula that won the FPAG 2003 green competition that uses 9% of it as the only binder and is meant to be dampened with water / alcohol which already changes things from red gum and phenolic resin in that regard, and they mention that 4% dextrin can be substituted which suggested that it's mainly functioning as a binder rather than a fuel and isn't a fantastic binder... it would likely protect against water / humidity better than dextrin though, and florida sits at 100% humidity around 364 days a year in some areas. I don't know what purpose the 50% water for binding given serves unless it's just to distribute the dichromate evenly over the Mg/Al and allow it time to passivate. It may ensure everything is coated with barium nitrate and make burning more even as well since that's soluble. You'd have to extrapolate from the other formulas what exactly the best uses might be. It should have a fairly high heat of combustion since the diterpenoids that are its primary constiuents are more saturated than phenols or dextrin, and this is kind of seen in the lower uses of it in the more blue baechle formulas (where red gum seems to be the main organic fuel) vs. hotter colors like amber. So I don't think it would be a great substitute fuel in most cases, definitely not more or less drop-in like phenolic resin seems to be for all colors, and phenolic has more flexibility as a binder even without thermo-setting, since these don't use it as the sole binder unless the percentage is higher. Someone who has used it might be able to tell you more, I was just interested in looking through to see what the best uses might be and couldn't find a great pattern. Edit: Baechle mentions vinsol can be substituted in for colophony, but this doesn't really imply anything about its usage in place of phenolics even though it had been used as an additive since vinsol is still apparently some sort of organic acid despite the name's implication of an alcohol. Colophony is mostly the diterpenoid abietic acid from what I can find, vinsol may just be a distillation of that to remove unpredictables. Edited February 14 by PyroGnome
PyroGnome Posted February 14 Posted February 14 Shellac doesn't work well with potassium perchlorate for whatever reason which is why it mostly shows up in chlorate formulas, ignoring that it usually costs more than red gum.
Mumbles Posted February 14 Posted February 14 Vinsol is a purified form of wood rosin. Whether raw wood rosin and colophony are the same, I've never been entirely sure. The overall process is that wood chips are extracted with multiple rounds of successive solvent extraction. This solvent is removed and recovered for reuse leaving the oils/tars/resins behind. The value added things like terpentine and more volatile oils are distilled off. The remaining non-volatile tars are left behind. This may be colophony. It is then further extracted to remove darker resins (oxidized) to produce a refined lighter color material. This lighter material is Vinsol. Apparently the darker material is deemed food grade and used in part to coat citrus fruit. https://www.ams.usda.gov/sites/default/files/media/waxes report rosin 2014.pdf With all these things being largely natural products or synthetic analogues their composition is somewhat variable and definitely complex. Making perfect substitutions is not always a straightforward task. Finding information on oxygen demand can be helpful in guiding replacements. What this really means is that 1g of red gum might require more or less oxidizer than shellac to burn cleanly. Substituting based on what's requires to burn cleanly tends to be a little more effective than simply swapping 1:1. 1
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