Hi everyone, I have a very recurrent defaults on my bronze castings, and have no idea where it comes from. I added 6 photos, the 1 is a photo of the global peace, the 2 is a zoom on the hairs of a perfect casting, and all the others are zooms on hairs that have porosity. I have casted tens of these and very often, I have very good results except on that part of the hairs (which is at the very bottom of the mold). I use a vacuum table. Thanks in advance for your help !
If your investment is heavier than the bronze (will not float), and since they are the bottom of the mold and intrude into the casting, I'd say the defects are likley caused by small broken pieces of mold washing to the bottom of the mold. The sprue is directly above and impinges on the hair features. If the hair has sharp creivices, those corresponding knife edges features in the mold are very fragile and could easily break as the heavy metal impinges on and washes over those features. Best, Kelly
Thank you for your fast answer. I have thought about it, but I use plaster for my molds, so it should float as it is lighter than bronze.
Looks like a combination of fire scale and loss of detail from possible spalling of the mold surface or wash out from the molten metal hitting that area as you pour. Need more information on how your doing the whole process to narrow it down. Are you using wax patterns or ?? What investment and how are you mixing it. Burn out schedule. Mold pouring temperature.
