The caulk/pumpable variety is a little hard to work with. I applied ~1/4" layers with a putty knife and let it dry, then fire. I was able to remove the foam plug before firing so it could be reused. I used paste wax as parting compound. But if you don't have much time into the foam plug, burn out is fine. Keep your caulk tube well sealed. If you ever break the cup or need to repair some damage, just fire it to about 1800F and it will remove any carbon and organics present from use, become a pristine white, and you can apply more where needed and re-fire.......good as new. The "moldable" version is thicker, like cookie dough and easier to model into shapes. If you don't have a Harbison Walker distributor available, I have occasionally seen it available at online sources here in the US. Agreed. I was quite pleasantly surprised when I started using them. Made a bigger improvement than expected. Best, Kelly
Could you explain it futher ? I tried to solve porosity eith some argon bubling. Ok on thin parts and first melt. Not ok with remelt.
There's an old saying: An ounce of prevention is worth a pound of cure. Bubbling Argon is the pound of cure. Tuning your burner to your furnace is the ounce of prevention. Molten Al absorbs hydrogen. If the amount of H2 in the Al gets too high it precipitates out into bubbles. This is what we want to avoid, visible porosity. Most of our burners are capable of introducing more hydrocarbons than the furnace can burn cleanly. There is only so much room in the furnace chamber so you have to control the amount of hydrocarbons introduced. With a naturally aspirated burner you can only open the valve so far before the flame becomes rich with hydrocarbons. Add a blower and that rich flame becomes lean. So, most people open the valve farther and the flame becomes rich again. Turn the valve down a little and you're back to lean. Lean flame equal less H2 for the Al to absorb.
Ok. Lean flame - only co2 and h2o plus some extra oxygen and full nitrogen. Rich flame result in some unburnt hydrocarbon. And it is easier to steal hydrogen from hydrocarbon than water ? Due to weaker bond ? But why some old foundries do not cast on wet weather due to hydrogen absorbtiom from moisture.. or it is much lower rate ?
