$9.29
CLICK THE "LEARN MORE ABOUT THIS ITEM" LINK JUST BELOW TO READ THE FULL DESCRIPTION FOR THIS ITEM.
*************************************************************
There are several materials that will retard the setting of plaster. This is a manufactured white powdered concentrated retarder which is probably a combination of several retarders. The supplier says 1/4 to 2 tablespoons per 100 lbs of plaster. It will also work with gypsum cements. They don't specify what type of retarder this is. The suppliers instructions are very simple:
"Retarder must be added to the water and should never be added directly to the plaster mix. By adding a small amount (1/4 to 2 tablespoons per 100 lbs of plaster), the setting time can be delayed up to one hour. Testing is recommended prior to full scale use. Results may vary. Excessive additions of retarder will drastically reduce strength, and many produce 'dry-out'. Use an appropriate dust mask when handling retarder."
As you can see, the amount of retarder needed is very low. The advice to make a small test is good, unless you're only making small amounts of mixed plaster in the first place! Here are some other smaller units if you're mixing way less than 100 lb of plaster or gypsum cement:
-- 2 tablespoons of retarder equals about 24 grams of retarder.
-- 100 lbs of plaster equals 45359 grams. Divide the grams of retarder (per 100 lb of plaster) you want by the number of grams in 100 lbs. That will give you a "conversion factor". It works out to 0.00053. Then multiply that conversion factor by the amount of dry plaster you're going to use.
An example using grams weight: If you were using the maximum amount of retarder (for the maximum working time of 24 grams of retarder per 100 lbs of plaster) for 100 grams of dry #1 pottery plaster you would multiply the conversion factor (0.00053) by 100 grams. That gives you an answer of 0.053 grams of retarder you should add to the plaster mix. Not very much! A digital kitchen scale set to grams would probably not be accurate enough to measure 0.053 grams of retarder. You would need a lab quality scale. (The amount of water you would add would be calculated separately. It varies with the type of plaster or gypsum cement).
One way to get around having to measure very small amounts of something is to dilute them in something that will be added to the mix. In this case water is the perfect candidate.
What you would do is make a retarder/water mix and add the retarder diluted in the water to the plaster mix.
Say you want a 1% amount of retarder dilution. Just measure 99 grams of water and add 1 gram of retarder and put it in a jar with a cap. Let it sit for a few minutes, mixing and/or stirring (mix it well each time you use it, because the retarder doesn't dissolve in the water, it will just sink to the bottom).
Using weight (as we did in the previous paragraph) is more accurate but in this case you could get by with volume because of the low percentage of retarder. Hopefully you have a measuring vessel that is marked off in ml or cc. Just measure 99 ml of water and add 1 ml of retarder (you can buy tiny measuring spoons that will measure ml).
Returning to the example of 100 grams of dry #1 pottery plaster, in which you need to add 0.053 gr of retarder. All you need to do is add 5.3 grams of the retarder/water mix to get the correct amount of retarder (you multiply 0.053 by 100). To be accurate you would subtract the amount of water you added when you mixed in the retarder/water from the total amount of water needed for a mix of 100 gram of dry #1 plaster.
One more comment about what kind of retarder this is. USG makes retarders and they are pretty common. I cannot guarantee this but it's possible this is USG's "retarder for plaster based products". Here is a data/instruction sheet for that retarder: { https://www.usg.com/content/dam/USG_Marketing_Communications/canada/product_promotional_materials/finished_assets/cgc-gypsum-plaster-retarders-data-sheet-en-can-P783.pdf }.
I haven't studied that sheet because I'm using the suppliers instructions (which is the safest thing to do) but if what they say as far as proportioning retarder to plaster, then that is a sign that this retarder is USG's "retarder for plaster based products". -
1-2 business days
I'll do my best to meet these shipping estimates, but can't guarantee them. Actual delivery time will depend on the shipping method you choose.
Buyers are responsible for any customs and import taxes that may apply. I'm not responsible for delays due to customs.
But please contact me if you have any problems with your order.
We're sorry, but at this time we do not ship internationally.
If you would like a smaller or larger quantity of a raw material, click the "Request a custom order" button and tell us how much you would like. Or just contact us and let us know what you'd like. We'll get back to you ASAP.
This problem usually occurs with multiple items. We have free shipping on many of our items. In your cart items will have the sum of all embedded shipping costs. If you place an order for 3 or more "FreeShip" items, you will receive a "rebate" for the excess shipping. The more items you have the greater the shipping refund will be. You can also message us to ask what the total cost of your order will be when excess shipping is refunded before you purchase.
Or, if you see "Request a Custom Order" or "Message Seller", you can request a custom order and your items will be put in a custom listing with the correct shipping. You would purchase it like any other listing.
If you have a technical question about an item we've listed, please don't hesitate to ask. We enjoy helping people out with a material or a process.
We give anecdotal information in our listings if we have any. If you disagree with it or think we're being inaccurate or misleading please let us know that, too.
If there are discrepancies in any of our listings let us know, we make mistakes like everybody and we'd like to be set straight and get those mistakes corrected.