Duplicate Model

[rebeccaterp]

After removing my duplicate model from hydrocolloid the model has a powdery finish to it. Almost like the stone hasn't set up regardless of how long I leave it there. It could be hours, minutes, or days.

Anyone know why?

The master model is fine. I blocked out all the undercuts with wax and immersed in cold water.

Can't figure it out.

Thank you

 

[araucaria]

Alum wash needed possibly. Potassium Aluminium Sulphate. (Not all Gels can be used without a wash). A solution needs to be made up and stored for the purpose. In my experience it's best to have this made up ahead of time for a better quality solution. Pour into mould and leave to stand for a few minutes - there are many opinions as to the timing of this. Pour out and blow off excess, then fill with your gypsum stone material. This should cure the problem.
Prior to pouring gel into the flask for the duplication procedure - soak in warm water, then blow off all excess before pouring gel. If the gel has been poorly handled or overheated, the performance qualities may diminish. If in doubt - contact your supplier for full details on how to get the best from the product.
hope this might help.

 

[CloudPeakDL]

Another thing is to watch your water powder ratio; to much water pools at the bottom causing issues.

 

[Mike2]

What I have found to cure this is applying a damp towel over the model as it cures. I believe the stone model is looking for moisture and is wicking the hydrocolloid into its surface. An older Dr. showed me that trick 15 years ago, I believe his name was Earl Wilcox. Anyhow I do this with all my models regardless of impression type and it seems to make harder more detailed models. The powder:H2O may be right but there is some wiggle room based on environment etc. Just damp enough to wring water out, not dripping wet. Hope it solves your problem!