I have recently been looking to replenish my supply of D5 (Decamethylcyclopentasiloxane) and did not have much luck receiving replies to my email. Others have reported difficulty finding this in quantities smaller than a 55-gallon drum.
I found a promising listing for cyclopentasiloxane and when I queried the supplier, he indicated that the analysis was 97.5% decamethylcyclopentasiloxane and the balance being octomethylcyclopentasiloxane. I suspect that is more than good enough for tape work.
The technique illustrated in this post is not as conserving of D5 as the technique I use for cassettes which is to use a hypodermic syringe to inject very small amounts into a cotton swab placed in the cassette shell on the supply side. So I thought I should purchase more. The up-side of the open-reel technique is that it’s very fast to set up and easily controllable. The downside is there is a small puddle under the heads, but this stuff evaporates and I was using one of the “second string” APRs. Also, the Sony APR-5000 series does not have many mechanical linkages that would be upset by excessive lubrication and its large-diameter ceramic capstan and hard-rubber pinch roller seem pretty immune to any issues relating to the D5.
Of course, I was looking for a Canadian supplier, but I was just assured that they also ship to the U.S.A.
http://www.aquatech-skincare.com/php_can/proddetail.php?prod=8181
Current pricing is $20.30 for a litre and $49.50 for 3.8 litres/1 U.S. gallon. It is some of the lower pricing that I saw and couple that with a friendly and accommodating staff, they got my money.
As an aside, the Canadian government has found no reason to regulate D5 at this point, despite some environmental groups issuing warnings about it. However, their conclusion is ambiguous and further monitoring is being undertaken. I would suggest getting a supply now rather than later if you plan on using it. I suspect my gallon will last me five to ten years or more. I would suggest good ventilation.
https://www.ec.gc.ca/ese-ees/default.asp?lang=En&n=13CC261E-1#a12
While all chemicals are a cause for concern, we use other chemicals that are dangerous (but in small quantities) including isopropyl alcohol and naphtha. Proper care is mandatory with all chemicals.