PR- can you change the "brittleness"

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RHunter

Local Chapter Leader
Joined
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Folks, I've been casting up a storm with Castin' Craft, Testors Paint, and the bottle recommended 4 drops per Oz of catalyst. 3 Oz or resin will fill a blank mold perfectly- so 12 drops of catalyst.

My blanks have been coming out a bit brittle. A good catch will shatter the blank.

Will more catalyst make the blank more or less brittle?

Or is this a factor that cannot be changed and I should be more careful turning?

TIA!

-Doug
 
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Less catalyst = less brittle, I believe...it increases curing time, but makes the blank 'softer'...

I believe Alumilite is softer still, so that might be the better bet for you.

Mind you, I don't cast myself yet, so take that with a grain of salt!
 
In my experience, the catalyst does not affect how brittle a blank comes out. The Castin' Craft tends to be a little more brittle to start with. I have never used the testors as a colorant, so I can't say if that impacts the Castin' Crafts outcome. After using many gallons of Castin' Craft and then going to Silmar, there is a hugh difference.
Just my $.02.
 
Ive been using oil based paints for a while but I use the paint from a tube and silmar. Ive found the paint softens the resin for me so when using paint i use four drops, but on a regular use, i only use three drops per ounce and havent had a problem, but thats silmar.
 
maxwell_smart007 said:
Less catalyst = less brittle, I believe...it increases curing time, but makes the blank 'softer'...

I believe Alumilite is softer still, so that might be the better bet for you.

Mind you, I don't cast myself yet, so take that with a grain of salt!
Click to expand...

This would be accurate. The more heat generated in the casting, the more brittle the resin matrix will be.
 
I am new to this and have been sourcing resin and pigments.
The supplier said that using TiO2 (Titanium Dioxide) powder instead of a white pigment will reduce the brittleness.
Haven't tried it yet so cannot confirm if he is correct. Bought some powder anyway.
 
I knew you folks would have some direction for me to try next.

I like the less catalyst, more cure time option. I put my casts in the PP and let cure overnight anyway, so what's a couple extra hours?

Thanks folks!

And based on the thread started by 'MostAngry'.... I just ordered a gallon of Silmar41 to use when I use up my Castin' Craft.
 
I haven't had trouble using Castin Crap (errr... Craft) with Testors enamel paints. No difference as far as I can tell.

Castin Craft really isn't that bad. But it is rather brittle. It's just expensive unless you have 50% off coupon for Michael's. ;)
 
DurocShark said:
It's just expensive unless you have 50% off coupon for Michael's. ;)
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Even with the coupon, it still costs more than Silmar, even after shipping and not as good in my opinion. Plus with CC you have to purchase the catalyst seperate.
 
It always has catalyst attached to the can when I get it. Anyway, I didn't say cheap. I said not expensive. 32oz can with cat for $15 means the difference between a silmar deal and this is like 50c per blank? Less? Not enough to sweat over.

But I agree about the quality difference. I got to turn a silmar blank recently and it was like night and day compared to Castin Crap.
 
Phil Hansen said:
I am new to this and have been sourcing resin and pigments.
The supplier said that using TiO2 (Titanium Dioxide) powder instead of a white pigment will reduce the brittleness.
Haven't tried it yet so cannot confirm if he is correct. Bought some powder anyway.
Click to expand...

TiO2 will bind with the Cobalt promoters used in most casting/thick laminating resins, and cause a cure inhibition. When using TiO2 you will have to increase the amount of catalyst to compensate.
 
DurocShark said:
It always has catalyst attached to the can when I get it. Anyway, I didn't say cheap. I said not expensive. 32oz can with cat for $15 means the difference between a silmar deal and this is like 50c per blank? Less? Not enough to sweat over.

But I agree about the quality difference. I got to turn a silmar blank recently and it was like night and day compared to Castin Crap.
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If you are paying $15 a quart, that's $60 a gallon. I just paid $45 for a gallon of silmar delivered to my door. The Micheal's we have sells the catalyst seperate for $6. It used to come with it under a cap on the top of the can, but no more.
 
Glass Scratcher said:
TiO2 will bind with the Cobalt promoters used in most casting/thick laminating resins, and cause a cure inhibition. When using TiO2 you will have to increase the amount of catalyst to compensate.
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This too is not true. Check the MSDS on any pigment and Titanium Dioxide is in it, not all, but most. This includes the Pearl-Ex pigments which most have used along with myself without any problems. There are two types of TiO2, oil dispersible and water dispersible. Either will work in our application.
 
DozerMite said:
This too is not true. Check the MSDS on any pigment and Titanium Dioxide is in it, not all, but most. This includes the Pearl-Ex pigments which most have used along with myself without any problems. There are two types of TiO2, oil dispersible and water dispersible. Either will work in our application.
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Pigments have varying amounts of TiO2. Small amounts can be accelerated over. However, organic pigments- many reds, and yellows, colors made with those reds and yellows will accelerate faster, so if they contain 5% TiO2 and 40% organics you will not see a degradation or inhibition in your cure.

However. a pigment that is the inverse, a large amount of TiO2 in its formulation and a small amount of organics, you will see a degradation or inhibition of cure. An increase in the amount of catalyst(MEKp) used will help to power through any inhibition that might be initiated by TiO2.

These arguments also need to be quantified with the total volumes of the pigment you are using, with the percentage of TiO2 contained, against the volume of resin you are casting as well as what type of resin being used. Silmar 40/41/5x are cobalt promoted at 3 parts per million, and the recommended pigmentation and filler load is 5% to 7%. Several of the casters are not using Silmar 40/41/5x, casting/lam resins, but are using Swing or Onyx resins. 5% to 7% is a rather light volume or filler load compared to what Swing and Onyx resins can be loaded with. Swing resins are heavily promoted (with other promoters in addition to cobalt naphthenate) to compensate for the volume of fillers and pigments that they may be loaded with.

Dozermite, you have stated over and over, and over again, that you cast HOT and your casts are fully cured and being turned in an hour. This indicates that you have used more than enough catalyst to compensate for any amount of TiO2 that may be in YOUR pigment formulations. You sir, are the exception to the rule. Those casters that ascribe to the "3 drops per ounce" will not have the same results as you.
 
I have never stated that I mix HOT. Just because it's cured in an hour doesn't mean the catalyst amount has been increased. There ARE other methods and I don't necessarily use the 3 drops per oz. rule that you may have. The instructions will even tell you to use 5-6 drops.
Yes, pigments do have different percentages of TiO2 and yet others have none. I have used many different brands of pigments and also resins along with several different colors and have NEVER had cure inhibition. I've also loaded, as you say, the resin with 25% pigment, by accident, and still no end result issues. Just a waste of pigment.
Everyone WILL have different results depending on many factors, some controllable and some not. So when mixing resins, these factors have to be taken into account, which means there is no need to get technical with measurements as what will work for you may not work for all. That is why everyone needs to use trial and error to find what works in their situation. Once a formula is found, repeatability is not a problem.
Casting is not rocket science and you don't have to be a chemical engineer to cast. Anyone can visit a manufacturer's website and acquire the information you pass along, however, not everyone is impressed with that ability. Knowing what does work is much more useful to an aspiring caster.
 
DozerMite said:
Casting is not rocket science and you don't have to be a chemical engineer to cast. Anyone can visit a manufacturer's website and acquire the information you pass along, however, not everyone is impressed with that ability. Knowing what does work is much more useful to an aspiring caster.
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No, casting is not rocket science or brain surgery, nor is it brain science or rocket surgery. You don't have to be a chemical engineer to cast either.

If many of the beginning casters would visit a manufacturer's website then many of the same questions that continually get asked would cease. Some of the information I pass on may be available from various manufacturers websites, but some is from spending hours talking to the techs at Silmar, AOC, Smooth-on, ETI,... and a fair amount is from my personal experience.

I am not, nor have I been trying to impress you, or anyone else. All I have done is try to impart information that can help others have successful casting experiences.

I am through with this thread. Any other comments can be directed to me offline.
 
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