Catalyst by Volume

[PTownSubbie]

I am wanting to get more consistency with my casts. I am currently using a drops/oz calculation when adding MEKP. Usually 3-5 drops/oz depending on conditions.

There are a few here (I think Charles & Bruce come to mind and I am sure more) that use a method of adding MEKP by volume rather than by drops/oz.

Can someone explain this method to me with some detail. I am sure this may be a question that when answered will be of more benefit than just to me.

 

[Sylvanite]

A friend of mine who used to be in the fiberglass business told me 1%-2% MEKP by volume of polyester resin. Depending on ambient temperature, humidity, additives, desired cure speed, etc., further adjustment may be needed.

Regards,
Eric

 

[NewLondon88]

Can't go by me .. I just squeeze the bottle.

 

[PTownSubbie]

A friend of mine who used to be in the fiberglass business told me 1%-2% MEKP by volume of polyester resin. Depending on ambient temperature, humidity, additives, desired cure speed, etc., further adjustment may be needed.

Regards,
Eric

My question is how do people measure the volume with that much accuracy?

I have some thoughts but it would be extremely complicated...

 

[RHunter]

Fred,

I measure my MEKP by transfering from the bottle to a 1ml or 5ml syringe (depending on the total volume of resin I am making).

I did the math based on the density of MEKP and figured out the drop/ml conversion and built a spreadsheet around it.

I plug in how much resin I'm using (also in ml), and it gives me the MEKP in ml to add.

I think I have that spreadsheet around here somewhere- but I think you just might need the drop-to-ml conversion- you can take the rest from there?

-Doug

 

[Glass Scratcher]

If you are going to measure by volume why convert to drops? There are 20drps to the mL by the way. Use metric ounces to measure your resin. 1oz is 30mL. If you cast say 4oz, that is 120mL. At 1% you would measure 1.2mL of catalyst. Use a 3mL syringe.

Here are my charts. You don't have to measure out to 2 decimal places.

 

[PTownSubbie]

If you are going to measure by volume why convert to drops? There are 20drps to the mL by the way. Use metric ounces to measure your resin. 1oz is 30mL. If you cast say 4oz, that is 120mL. At 1% you would measure 1.2mL of catalyst. Use a 3mL syringe.

Here are my charts. You don't have to measure out to 2 decimal places.

Thanks Charles! That is the direction I was headed. I was thinking that a mL is a mL regardless of what the fluid is and mL is a measure of Volume...

Does your conversion factor of 1oz is 30mL vary is I am using Silmar 40 vice 41 or do I have to measure an oz of it to verify?

I am going to give it a shot. Just have to find the syringes now. Any ideas on a good local place? Can you get them over the counter at drug stores?

 

[Glass Scratcher]

Thanks Charles! That is the direction I was headed. I was thinking that a mL is a mL regardless of what the fluid is and mL is a measure of Volume...

Does your conversion factor of 1oz is 30mL vary is I am using Silmar 40 vice 41 or do I have to measure an oz of it to verify?

I am going to give it a shot. Just have to find the syringes now. Any ideas on a good local place? Can you get them over the counter at drug stores?

1 liquid metric ounce is 30mL. 1 US liquid ounce is 29.574mL. The .426mL difference is negligable, so just use the 1 metric ounce (moz) = 30mL for simplicity.

For measuring volume- a liquid mL is a liquid mL. If we were measuring by weight yes you would need to measure and weigh out the amount of resin, just as if you were using a urethane. Silmar 40 vs 41 probably does have different molecular density, but again we do not need to weigh it.

I get syringes from the medical supply house, I buy the syringes and needles separatly. I use the 23g needles for drawing pigments, and 27g needles for MEKp. I like the Luer-Lok syringes as you can remove and reuse the needle in your MEKp. The rubber on the plunger will break down in a week from the MEKp. When I cast, after drawing and dispensing the MEKp, I withdraw the plunger some, and replace the needle sheild and stow the syringe needle down. Any remaining catalyst will drain into the needle and sheild and not erode the rubber so much. You can probably buy them online cheaper, remember to factor in s&h. You may be able to get them over the counter depending on which state you live in. In Florida a prescription in not required.

 

[NewLondon88]

Does your conversion factor of 1oz is 30mL vary is I am using Silmar 40 vice 41 or do I have to measure an oz of it to verify?

The Glassman has it, but I know it can be confusing because an ounce
is a unit of weight .. but a fluid ounce is a measure of volume. Go figure..

 

[PenMan1]

All gpod stuff Charles! Thanks for the charts!

 

[PTownSubbie]

Alright, the lightbulb came on...

The 1oz=30mL is nothing but a conversion factor...

So here is the procedure:
1. Measure out the amount of PR I want to use.
2. Weigh the PR in Oz
3. Multiply the Oz by 30 to get mL
4. Multiply this value by 0.01 to determine the amount of MEKP to use in mL
5. Draw the amount of MEKP into the syringe
6. Dispense the syringe into the PR and mix

Does that sound right?

BTW, what kind of liquid dyes are you using that you can draw into a syringe?

 

[Glass Scratcher]

Alright, the lightbulb came on...

The 1oz=30mL is nothing but a conversion factor...

So here is the procedure:
1. Measure out the amount of PR I want to use.

********2. Weigh the PR in Oz

3. Multiply the Oz by 30 to get mL
4. Multiply this value by 0.01 to determine the amount of MEKP to use in mL
5. Draw the amount of MEKP into the syringe
6. Dispense the syringe into the PR and mix

Does that sound right?

BTW, what kind of liquid dyes are you using that you can draw into a syringe?

Don't worry about weighing any of the PR. Just measure out the liquid resin and multiply for conversion.

drop step 2.

You may want to use, for calculating the MEKp for S40, o.75% or o.o75, as S40 accellerates to a higher temp. Remember you have a play of +/-o.5% for your ambient temp.

I use the paste pigments from US Composites, and from Surfsource surfboard supply, and Mixol. Because they are a paste pigment you have to use a larger diameter needle to draw them. Kinda like sucking on a thick milkshake with a thin straw. I only base pigment with the pastes, I then fill color with the powders. I use powders from Coastal Scents, and Pearlex.