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nc42
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Unfortunately the road to knowledge in the composites and mold making world is paved with money!
That said don't write off Smooth-on. I've used many of their products in the past and they make quality products and usually have above average customer support. Also in the technical data and the product info page it does say "These products have a limited shelf life and should be used as soon as possible." Might be an expensive lesson but let it be a lesson to read all the available information on what ever product you're looking to use, maybe read it 2 or 3 times!!
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TURK
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nc42 (12/01/2017)
Unfortunately the road to knowledge in the composites and mold making world is paved with money!
That said don't write off Smooth-on. I've used many of their products in the past and they make quality products and usually have above average customer support. Also in the technical data and the product info page it does say "These products have a limited shelf life and should be used as soon as possible." Might be an expensive lesson but let it be a lesson to read all the available information on what ever product you're looking to use, maybe read it 2 or 3 times!! Absolutely nc42, quite agree ......... Read, and re-read the products DataSheet 'before' you place an order ....... and not after you've placed your order as I did !  With the products datasheet set aside for when I would need it, the day that I would need to work out the mixing ratio's ......... not only is that shear stupidity, but as you say ...... a very expensive lesson learned ! You're absolutely right about not righting off 'Smooth-On, their technical staff were very helpful and straight onto the problem right away. As they informed me that they did occasionally have 'bad batches' of the the product, the batch number or LOT number soon showed mine wasn't, but still agreed that they were going to give me 10% discount if I should re-order some more.
I was tempted .......... but I also really needed to know how good the CS25 was from EC, so I ordered that. I will still use the OOMOO product in future projects, but not projects the size of this one. As OOMOO 30 ( or 25 ) are very expensive. So as a cost saving exercise I ordered the CS25 from EC. While I was there, I ordered myself the full degassing system  This way, I'm not tied down to using products that are considered 'degassing not necessary', and I can of course use the system for resins >>
Quick question on the RTV silicone if I may ......... I placed an order for 'CS25', but it says 'CS2' on the containers. I know from reading EC' website that the CS25 is a newer formula ....... so what did I actually get ? |
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Rich (Staff)
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Hey Pascal, you do have the latest generation of Condensation Cure Silicone 'CS25' - we just haven't updated all of the packaging labels yet. The CS25 comes with a black catalyst which I can see in your photograph.
Sorry for any confusion.
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TURK
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Rich (Staff)
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You require 5g of Catalyst for every 100g of silicone, therefore you have 20 x 100g (2,000g) of Silicone and would need 20x5g of catalyst accordingly. 2000g Silicone = 100g Catalyst. Your maths is right 
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TURK
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Rich (Staff)
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there are lots of ways of working out so long as you arrive at the correct amount, that's al lthat counts.
The other way to consider it is that you need 5% of the total quantity of silicone so 5% of 2000g is 100g.
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TURK
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Hi all, Just in case somebody is interested, with reference the EC Vacuum degassing system ......... I asked the question if it were possible to utilise the vacuum chamber on it's side, horizontal as it were, on EC's website. Like this >>  Some people may be begging the question why !? ........ well this is the point I was trying to make. While reading how to effectively degas silicones and resins, I read that sometimes for better results, that a second degas is preferable. So it means you have to put your entire mould set up box in the vacuum chamber .......... as I'm making moulds for a headlight assembly, my moulds are more of a 'shoebox' shape. This is just a temporary set up just for the picture, but you get the idea >>  Obviously you would have to make an insert and make sure it were level, and you would have to secure the lid. I was planning on using straps, like the ones you get for luggage. Unfortunately, my mould boxes are 5mm too long !  never mind, I'll know for next time. But at least it's good to know.
Just one other thing, I assume the gauge would still work accurately positioned like that ?
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TURK
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Why have my pictures been reduced to the size of a postage stamp !? They were 900 x 600 when I uploaded them. TURK
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Hanaldo
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Just on the topic of calculating catalyst ratios, thought I would add my formula to the mix in case it helps. As Richie said, there's a thousand ways to work it out and as long as you get the correct answer then none of them are wrong, but this is the way I find the easiest. As you are looking for a percentage, you can simply divide by the ratio given. So if you need an exact quantity, pets use your example of 2000 grams of silicone, then simply divide by 1.05. This gives you the amount of silicone that you need to pour, which in this case is 1905g (1904.76 if you don't like to round up). You can then taken that number from your required amount to work out how much catalyst you need; 2000g-1905g = 95g. In the case of the CS25, 5% isn't a whole lot of wastage so you can just say ok well I need 2000g so I'll just pour 2000g and then add 5% catalyst and end up with 2100g as you did with your calculation. However I find this way easier because you can use it for whatever mix ratio you are given. So say for the VacCast epoxy resin system that you want to use to form your actual moulds, this mix ratio is 100:6 (not a whole lot different to 5% I know, but for the sake of sticking with products you are using!). So if you need 1500g to pour your moulds, you simply do: 1500 divided by 1.06 = 1415g of part A. And then 1500-1415 = 85g of part B. You can also manipulate the formula to solve any errors you make pouring the stuff. So say you need 1500g of the VacCast in total and you already worked out that means you need 1415g of part A, but then you accidentally pour a bit much and end up with 1484g of part A. Now you could try to tip the excess back into the container and end up back at your original amount, or you could reverse the equation and solve for how much hardener you need for your new amount: 1484 multiplied by 1.06 = 1573. 1520-1484 = 89g of Part B.
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