Smoothing masters for molds

[mycapt65]

Hi, 

I'm new here. I've been making soft plastic lures for saltwater stripers for a couple of years now. My latest design is a paddle tail. The master is made of sculpy oven hardening clay. I want to smooth out the blotchy texture and sanding marks with some primer like paint or coating but I don't know what's safe to use with the two part silicone. Any suggestions would be great. 

Thanks Ron

[seakarp]

You could also drop down to a finer sand paper, like say 220 grit.

[Travis]

After sanding until smooth I will spray with shellac.

 

[mycapt65]

3 hours ago, seakarp said:

You could also drop down to a finer sand paper, like say 220 grit.

Thanks. I've dropped the grit to 240 but the clay has a weird grain that won't sand out. So I have to fill and sand the filler flush. It's really not necessary but I want it to look nice. 

[mycapt65]

42 minutes ago, Travis said:

After sanding until smooth I will spray with shellac.

 

Very nice! what kind of shellac do you use. I've thought about using a clear water based Polyurethane. Have you tried that? 

[Travis]

I used Zinsser Spray shellac as easy to apply, dries within minutes, and sands easily and can build coats no problem.  

Wood filler can also be used to get a final smooth bait.  Once the master is made you can just use your finger and wipe problematic areas with the wood filler and sand once set up may help to thin slightly with water.   Don't need anything  high end and Minwax products easy to get at most big box stores. Can also mold up areas with the wood filler very easily to make changes.  Durham's water puddy can also be used in the same fashion but doens't smooth as easy.

The goby below used these techniques. The lighter color observed around the lips, eye socket, and pectoral were all adjustments made with wood filler.  

 

 

Edited January 9, 2021 by Travis

[Bass-Boys]

Travis,,

Is that picture really from 2006?

[Bass-Boys]

3 hours ago, mycapt65 said:

Thanks. I've dropped the grit to 240 but the clay has a weird grain that won't sand out. So I have to fill and sand the filler flush. It's really not necessary but I want it to look nice. 

220-240  seems pretty course for final sand to me ?? 

[Travis]

1 minute ago, Bass-Boys said:

Travis,,

Is that picture really from 2006?

Yeah the date should be pretty close.  The month is off by a few but the year is correct.   

[mark poulson]

54 minutes ago, Travis said:

Yeah the date should be pretty close.  The month is off by a few but the year is correct.   

That is a really nice bait.  Years after you did it, I made some sculpin molds with Sculpy clay, and they got bit down in SoCal.  Here's a link to the 4" version:  

 

[SlowFISH]

For awhile I was finishing rapid prototypes and using them to make silicone molds... and rapid prototypes have build lines all through it - so required alot of sanding.

If you really want to super smooth - you'll probably need to use a auto primer (spray can is fine) and wet sand down in steps from 240 to a 1000 grit - even finer if your picky.  Even at 600 grit you'll still see lines picked up with a silicone mold - silicone is unforgiving and is usually formulated to pick up the fine details.  I'd wax/buff the hell out the to part create a layer of protection between the part/paint and mold material.

Unfortunately - I can't tell you exactly what brand of paint to use - as type of paint and type of silicone is all different.... and some can react differently - obviously testing a small item first is best bet.  If you buy your silicone from a place like SmoothOn - give them a call - they are helpful and might know a product that is compatible with their materials.

J.