Best Way To Smooth Out Rtv In A Mold?

[Kasilofchrisn]

I had a request to modify one of my molds slightly.

Decided red RTV was the ticket to accomplish what I needed to do.

So it woks well now but the RTV isn't really smooth like I want it to be. It will work for now though.

When you guys apply RTV to a mold is there a good way to smooth it out.

The ways I tried it just sticks to whatever tool I use to accomplish the task and is hard to get it looking perfect.

Is it better to wait until it partially sets? Or should I oil the tool first so the RTV doesn't stick to it?

I'm open to suggestions.

Edited July 15, 2015 by Kasilofchrisn

[goodtimesfishing]

In most situations I let the rtv set up and then cut with razor blade. If situation doesn't allow for that, I wet my finger and smooth it out. Wet whatever tool you use and it will be less likely to stick.

[Vodkaman]

If the master is bottom mounted and the RTV poured over, then the finish is not important. A few heavy taps of the mold container onto a solid surface should level the RTV out and let gravity do the rest.

I have never tried top molding, by sinking the master into the surface. This method, although an accepted method, just seems too imprecise to me. But, an imperfect surface would be a plus, as every imperfection is adding a good location key, so I wouldn't be too bothered about smoothing out.

It is nice to finish up a mold and have it all looking pretty and squared off. In my early attempts at plaster molding, I would sand the surfaces and sides. Yes, the molds looked pretty, but they did not perform any better and once I stopped, I didn't have to buy 20 sheets at a time and spend ten minutes cleaning up all the plaster dust.

Dave

[Kasilofchrisn]

In most situations I let the rtv set up and then cut with razor blade. If situation doesn't allow for that, I wet my finger and smooth it out. Wet whatever tool you use and it will be less likely to stick.

That's most likely what I will do in the future when I find time. I have a bunch of small exacto knife blades.

It's a rather large Aluminum CNC mold. The goal is to add just a bit of the RTV so the #3 line tie eye stands out a bit more than it originally was designed to.

To make a little more room to hook on a large swivel in addition to the assist setup I normally use.

Edited July 16, 2015 by Kasilofchrisn

[Kasilofchrisn]

If the master is bottom mounted and the RTV poured over, then the finish is not important. A few heavy taps of the mold container onto a solid surface should level the RTV out and let gravity do the rest.

I have never tried top molding, by sinking the master into the surface. This method, although an accepted method, just seems too imprecise to me. But, an imperfect surface would be a plus, as every imperfection is adding a good location key, so I wouldn't be too bothered about smoothing out.

It is nice to finish up a mold and have it all looking pretty and squared off. In my early attempts at plaster molding, I would sand the surfaces and sides. Yes, the molds looked pretty, but they did not perform any better and once I stopped, I didn't have to buy 20 sheets at a time and spend ten minutes cleaning up all the plaster dust.

Dave

This is a simple modification of an Aluminum CNC machined mold that I am working on.

I haven't yet made a mold out of RTV.

[Vodkaman]

This is a simple modification of an Aluminum CNC machined mold that I am working on.

I haven't yet made a mold out of RTV.

Yes, I spotted that after writing the post, realizing I had misread the original. Rather than throw it away, I decided to act dumb and post it anyway. What I should have done was started a new thread with it.

The razor is obviously the way to go.

Dave