Latex vs Silicone

[LCF]

It's difficult to get a sheet of .006" or .004" latex any wider than 6" where I live. I have liquid latex so have been developing my latex brushing skills on glass. Meanwhile I have found a vendor with 500mm square sheets of 0.1mm (0.004") and 0.2mm thick sheets of silicon rubber.  

Any opinions as to whether this would be suitable for casting plaster forms?

[Brad Dorsey]

I cannot comment directly on using sheet silicone when making plaster casts, because I have always used sheet latex.  But I have observed that the flexibility of the latex makes it very well suited for this use, because it can stretch to tightly conform to the arching of the plates.  So, if the silicone has the same flexibility as the latex, I think it would be equally well suited.

[LCF]

It was cheap, around $au10 ea, so I'll find out soon!

[Guido]

I use a type of cling wrap. But not the common kitchen variety.

It comes in thicker/stronger versions on larger/wider rolls and is commonly used for pallet wrapping.

I find it just about perfect. And it’s cheap and readily available. I had trouble finding suitable latex where I am, too.

[LCF]

2 hours ago, Guido said:

I use a type of cling wrap. But not the common kitchen variety.

It comes in thicker/stronger versions on larger/wider rolls and is commonly used for pallet wrapping.

I find it just about perfect. And it’s cheap and readily available. I had trouble finding suitable latex where I am, too.

Thanks!

[Brad Dorsey]

4 hours ago, Guido said:

I use a type of cling wrap... [that is] commonly used for pallet wrapping.

That sounds like something I might want to try.  Where do you get it?  Is it available in small amounts?

[Mark Norfleet]

2 minutes ago, Brad Dorsey said:

That sounds like something I might want to try.  Where do you get it?  Is it available in small amounts?

I’ve only ever seen and used it on rather large rolls.  I think it would work ok for my purposes, but it isn’t as stretchy as the latex we commonly use.

[Jerry Lynn]

Latex per meter in the Netherlands ships world wide.  I know that it's going to be crazy expensive to ship to OZ, but latex works really well and can last a long time if you take care of it.  

[Guido]

10 hours ago, Brad Dorsey said:

That sounds like something I might want to try.  Where do you get it?  Is it available in small amounts?

Don’t remember where I got it. Random online. There are different width roles, my wrap is 50cm wide.

Smallest amount available is a lifetime supply though.

I like how thin it is given the strength.

[Guido]

57 minutes ago, Jerry Lynn said:

Latex per meter in the Netherlands ships world wide.  I know that it's going to be crazy expensive to ship to OZ, but latex works really well and can last a long time if you take care of it.  

It can be surprisingly ridiculous to get stuff shipped to OZ. I gave up when I was looking for latex (a while back).

[LCF]

14 minutes ago, Guido said:

It can be surprisingly ridiculous to get stuff shipped to OZ. I gave up when I was looking for latex (a while back).

Yup.

A small parcel from the US can easily cost 100$, versus the silicone sheet I just ordered from China which had minimal postage. 

[LCF]

1 hour ago, Guido said:

Don’t remember where I got it. Random online. There are different width roles, my wrap is 50cm wide.

Smallest amount available is a lifetime supply though.

I like how thin it is given the strength.

 

Bunnos have "Wrap & Move 500mm x 280m Clear Pallet Shrink Wrap"

$20 for 280m!

Does that sound like the stuff?

[Guido]

3 hours ago, LCF said:

Bunnos have "Wrap & Move 500mm x 280m Clear Pallet Shrink Wrap"

$20 for 280m!

Does that sound like the stuff?

Looks perfect. They didn’t have that when I was shopping around for mine a while ago.

[Jerry Lynn]

12 hours ago, Guido said:

It can be surprisingly ridiculous to get stuff shipped to OZ. I gave up when I was looking for latex (a while back).

I totally get it.  I suppose a lot depends on what you are used to.  Despite having other materials and methods available, I still prefer using latex as a barrier for general casting.  I’d be willing to spend a great deal for its convenience and function. 

[lFred]

If I recall correctly @christian bayon at Schimitt lead paper/film was used.  I do recall it was a metallic film of sort but doubt it was aluminium, as from my souvenir it did  not wrinkled.

[David Burgess]

5 hours ago, lFred said:

If I recall correctly @christian bayon at Schimitt lead paper/film was used.  I do recall it was a metallic film of sort but doubt it was aluminium, as from my souvenir it did  not wrinkled.

Yes, lead foil was about the best thing around when I first got into the restoration business about 50 years ago. It was highly malleable and formable, so it could be formed to follow compound curvatures without wrinkles, with the help of a little mild adhesive (usually a thick linseed oil) between the foil and the instrument part being plaster-cast. Done it many times.

I think that using thin latex sheet is a whole lot better. For instance, it will conform to the shape of the part quite well with the weight of the plaster alone, without requiring any greasy adhesive which can contaminate cracks.

Things like "plastic wrap" don't conform quite as well to complex shapes, so have a greater propensity to produce wrinkles.

[Brad Dorsey]

1 hour ago, David Burgess said:

…thin latex sheet…will conform to the shape of the part…with the weight of the plaster alone, without requiring any greasy adhesive which can contaminate cracks...

I really like the latex for this reason.

[LCF]

43 minutes ago, Brad Dorsey said:

I really like the latex for this reason.

The pallet wrap is heavier than regular shrink wrap and a bit stretchy. (You often will have seen it stretched around square pallets of goods.)  I think it's polyethylene. Thickness is approx 0.8 thou 0.0008"  which might be good for fine detail. It can be draped over a plate ok. I'll see how it goes with plaster.

I think when my 0.1mm and 0.2mm  silicone sheet arrives it will be comparable to latex without some of the problems since it is completely  inert. 

My son bought some urethane based bicycle tubes recently. These are very thin and obviously stretchy and strong. If that is available in flat sheets that would probably work too and last forever. 

[Mark Norfleet]

22 hours ago, David Burgess said:

Yes, lead foil was about the best thing around when I first got into the restoration business about 50 years ago. It was highly malleable and formable, so it could be formed to follow compound curvatures without wrinkles, with the help of a little mild adhesive (usually a thick linseed oil) between the foil and the instrument part being plaster-cast. Done it many times.

I think that using thin latex sheet is a whole lot better. For instance, it will conform to the shape of the part quite well with the weight of the plaster alone, without requiring any greasy adhesive which can contaminate cracks.

Things like "plastic wrap" don't conform quite as well to complex shapes, so have a greater propensity to produce wrinkles.

I do believe that it was tin foil, and not lead.  It is still available from dental supply places in a few different thicknesses.  The thinnest I found with a quick search was .001”/.025mm.  I have it in my memory that the stuff we used was thinner, but don’t know for sure.  
The Weisshaar book mentions .0006” tin foil.

[Jeffrey Holmes]

1 hour ago, Mark Norfleet said:

I do believe that it was tin foil, and not lead.  It is still available from dental supply places in a few different thicknesses.  The thinnest I found with a quick search was .001”/.025mm.  I have it in my memory that the stuff we used was thinner, but don’t know for sure.  
The Weisshaar book mentions .0006” tin foil.

If you're speaking of the stuff we used at "the firm", I believe you are correct.

I still have (and very occasionally use) a roll of tin foil (.0006 if memory serves me) I bought from Cremona Tools years ago. It's wider than any I could find in the states at the time. I looked for it on their site today, but could not find it there. May be a discontinued item.  I do recall it wasn't cheap.

Frankly, 99% of the time (maybe I'm exaggerating?  Maybe not!) I'd rather use thin latex. We ordered some to be split for interested workshop participants  at Oberlin several years ago which was thinner (at .004) than what is commercially available (at .006) which was nice, but it was more fragile... and the minimum run was $500 at the time. May order more in the future. I find the .006 works fine for most jobs, however.

The Definition/detail with latex can be improved a bit with a vacuum setup (didn't know if anyone had mentioned that earlier in the thread).

Some restorers (like Jean-Jacques Fasnacht) make their own ultra thin latex sheeting.

[LCF]

1 hour ago, Jeffrey Holmes said:

If you're speaking of the stuff we used at "the firm", I believe you are correct.

I still have (and very occasionally use) a roll of tin foil (.0006 if memory serves me) I bought from Cremona Tools years ago. It's wider than any I could find in the states at the time. I looked for it on their site today, but could not find it there. May be a discontinued item.  I do recall it wasn't cheap.

Frankly, 99% of the time (maybe I'm exaggerating?  Maybe not!) I'd rather use thin latex. We ordered some to be split for interested workshop participants  at Oberlin several years ago which was thinner (at .004) than what is commercially available (at .006) which was nice, but it was more fragile... and the minimum run was $500 at the time. May order more in the future. I find the .006 works fine for most jobs, however.

 

It is always interesting to hear about these things!

 

1 hour ago, Jeffrey Holmes said:

The Definition/detail with latex can be improved a bit with a vacuum setup (didn't know if anyone had mentioned that earlier in the thread).

Vacuum was mentioned by Brad Dorsey in his essay and a vacuum connection is part of my planned baseboard as an option, by routing a suitable channel.

 

1 hour ago, Jeffrey Holmes said:

Some restorers (like Jean-Jacques Fasnacht) make their own ultra thin latex sheeting.

In this latex thread @fiddlecollector described brushing out latex on glass:

latex sheet

 

 

Inspired by that I tried similarly and my second attempt was reasonable, att below. But brushable latex is a tricky substance in my climate, it coagulates even if you look at it  wrongly and destroys brushes. I do not trust that it will not have pinholes. Perhaps I'll try again in autumn. If I didn't already have the latex for other casting projects it would have cost too much anyway.

 

Otoh the 0.1mm silicone sheets are available cheaply and conveniently on ebay. 

0.1mm-1mm Silicone Rubber Sheet 500x500mm 500x1000mm Transparent Silicone Film | eBay

https://www.ebay.com.au/itm/304699236423

Those could be dusted if necessary.

 

[Mark Norfleet]

34 minutes ago, LCF said:

Otoh the 0.1mm silicone sheets are available cheaply and conveniently on ebay.

I bet the silicone will work just fine, so long as it has enough strength to resist tearing at the F holes.  If you’re attaching the plate to be cast to a piece of plywood or other such base, be sure to leave a hole through it to allow air to be expelled so you don’t get any surprises.  I very much doubt using vacuum will get you any worthwhile improvement using a parting film that thin.

[Jeffrey Holmes]

1 hour ago, LCF said:

 

Vacuum was mentioned by Brad Dorsey in his essay and a vacuum connection is part of my planned baseboard as an option, by routing a suitable channel.

 

In this latex thread @fiddlecollector described brushing out latex on glass:

 

I tend to review most all of the ongoing threads, usually have limited time,  and therefore I am certainly guilty of not reading all threads start to finish carefully.  My apologies to Brad and fiddlecollector.

 

[fiddlecollector]

10 hours ago, Jeffrey Holmes said:

I tend to review most all of the ongoing threads, usually have limited time,  and therefore I am certainly guilty of not reading all threads start to finish carefully.  My apologies to Brad and fiddlecollector.

 

No need to apologise, LCF brought it up from years ago. I found it ok making latex sheet but it is difficult to get right thickness and i had the opposite problem to LCF i had to use a hair dryer all the time to get it to dry.

I was putting a TPU screen protector on my phone yesterday ,has anyone used TPU film , seems to have some good properties if you can find right thickness?

[LCF]

2 hours ago, fiddlecollector said:

I was putting a TPU screen protector on my phone yesterday ,has anyone used TPU film , seems to have some good properties if you can find right thickness?

The bike tube my son bought is tpu thermo plastic urethane and it is superthin  and tough but opaque. It turns out there are several different types of urethanes involved. One of them is made into a clear plastic film for putting over your car to protect the paint similar to those screen protectors.