Roto-Casting Question


Sr Member
I am relatively new to roto-casting and I'm having a small problem. I am roto-casting in multiple layers, but I'm getting some delamination between the layers. I'm using Smooth-on smooth cast 65D. I checked the tutorial on the smooth on site, but they are doing one thick coat instead of multiple thin coats. Should I just do one thick coat? If I do multiple coats do I do the coats one right after the other? Does each coat need to be fully cured before the next one? Any help would be greatly appreciated. Thank you.
I do mine in thin layers because when i use too much it makes a mess when it starts to thicken. Do all the layers quickly after the last one. I do mine a couple minutes after it turns completely white. If it cures all the way it will not bond to the last layer. I tried another layer the next day once and it could be peeled right out after it hardened. It didn't bond at all. I also use the 65D. Hope that helps.

I haven't done any rotocasting (would love to...making a machine is on my list of summer projects), but definitely agree with smurf, you don't want the layers to fully cure, or you'll see the delamination. I do a lot of slush casting with 65D, and once it's cured, that's it. If I find out later that I have a spot which is too thin, it's difficult to correct. I've had mild success with sanding an area, and then adding more resin, but of course that's not possible on a hollow cast.
Last edited by a moderator:
You do not wait until the previous layer cures before proceeding to the next. Wait until it isn't runny and turns white and you are ready for the next coat. A fresh layer of 65D will not stick permanently to a fully cured layer and that is why yo are getting delamination. Also, doing this is a hot environment quickly speeds up the cure time as well, so take that into consideration.
If you are using a two-part closed mold, I recommend laying up or slush cast the first layer. Then when the resin is in a paste kind of state, Pour in a couple more ounces of resin and seal up the mold to be rotocasted.

Be sure to read the instructions of your resin. If its a 2 minute cure, be sure to pour the next batch at a minute and a half. As Cunningham stated, weather can play a role in the curing process so experiment.
This thread is more than 8 years old.

Your message may be considered spam for the following reasons:

  1. This thread hasn't been active in some time. A new post in this thread might not contribute constructively to this discussion after so long.
If you wish to reply despite these issues, check the box below before replying.
Be aware that malicious compliance may result in more severe penalties.