Sometimes getting slurry to bond to wax when dipping can be a bit difficult. Depending on the surface and texture of the wax, the initial coats can go on a bit patchy, requiring several dips before an even layer of sand can be applied. Cleaning the wax with lighter fluid before dipping helps. Dipping a the wax in the slurry a few times to build up an initial layer of silt helps too. With the latter however, small stalactites of slurry mix can form on the wax where it drips and I'm unsure of their structural properties. I've heard that adding sodium silicate to silicate binding agent is a good way to create a dip that builds up an initial layer on the surface of the wax. However, I can't find any information about what sort of mix ratio this needs. Has anyone tried this method? How did you find the results? And how much sodium silicate per litre of binding agent should you use?
I found the thin patchy initial layer is not an issue. I let it dry thoroughly spray it lightly with binder then apply a second coat of slurry allow this to dry also, then followed by the slurry stucco layers. Ive found that the wetting the shell with binder before applying each layer results in a strong bond between layers. In the early days I used to apply slurry to dry shell and I often had problems of the layers separating in some areas at burnout, especially the thin first couple of layers
Yeah, I usually do a slurry dip and let it dry between adding layers of stucco, at least for the fine grain at the start and the very end. I have seen sodium silicate used before though, but whenever I've asked about it I've gotten crickets. I've seen recipes that use it during patination to seal the finish between coats too. In all it seems like it might be useful tool, but it's a mystery to me how to use it properly.
Wish I knew. From what I've read, it sounds like to apply patina over the solution during heat treatment, using the sodium as a fixative. This foundry uses it in all their recipes but don't go into much detail. https://mckinneyfoundry.com/patination-recipes-resource. Seems like they add the sodium into the patina solution as well as artist pigments.
I see some type of pre-dip in this prosses for stainless steel jewelry shell casting.. Maybe it has something to do in aiding the clean up.. Stainless steel ring casting process | CF Jewelry - Bing video
Cool video, but I didn't see them using a pre dip. Unless the liquid they placed the sprue in after it was extruded was more than meets the eye. But my guess is it was just water.
The first two dips were of a different color, and there was not much of a time lapse between them.. I was assuming they were of a different nature. I was thinking that the first dip might contribute to a better removal of the last few coatings.
