Solubility of PVA Filaments

Hi.

I am using PVA as a tool for silicone mold making. I print an object with PVA, cover it with silicone and then dissolve the PVA, which creates a silicone mold of the object. So far, the most problematic part is the dissolving part. I only had access to PVA by Esun and it simply doesn't want to dissolve. I have bought an ultrasonic bath and use hot water to speed up the process combined with ultrasonic cavitation. What happens is that the filament softens but still requires me to manually take it apart. The problem is that the surface area of the object in contact with water is very small, as most of the object, except it's poles, are covered with silicone. In YouTube videos PVA seems to be dissolvable like it is effervescent but in reality it doesn't behave like that. This is the kind of behavior that I need, because if the dissolved part doesn't disappear completely, there is no way the water is going to be able to penetrate the inner parts.

My question: Do you know a more soluble brand? Or how can I enhance solubility?